Sandbox / Arkham Horror LCG

General mechanics and recurring tropes

• Manipulating the Opponent's Deck:

---

NotZ

• Manipulating the Opponent's Deck:

TDL

• Manipulating the Opponent's Deck:

Pt C

• Manipulating the Opponent's Deck:

TFA

• Manipulating the Opponent's Deck:
• Scaled Up:
  • "Curse of Yig" treachery (from Agents of Yig encounter set), on top of its actual effects (reducing your Combat and Health by 1), also gives investigator Serpent trait, but it's purely cosmetic, as nothing in the game actually references it. Going human again is possible, but you have to pass Willpower test, which can easily become impossible if you accumulated too many vengeance points during the scenario, as the test's difficulty scales with their amount.
  • Towards the end of campaign, Ichtaka betrays the investigators and attacks them (unless they fulfilled conditions to keep her as a friend), trying to steal the Relic of Ages; the next time, they would see only in the final scenario, where she would turn into serpent woman.

TCU

• Manipulating the Opponent's Deck:

TDE

• Manipulating the Opponent's Deck:

TIC

• "Get Back Here!" Boss: The Amalgam (from "The Pit of Despair") can't be defeated, only temporarily forced to retreat into depths, which allows to take back whatever keys it had stole. However, it can also sink through effects of encounter cards, not dropping the keys, making you wait for it to resurface again (those same cards, is they can't make it sink, do the opposite instead).
• It Only Works Once: To resign in "Devil Reef" scenario, you must be in the boat at the time, and resigning also removes the boat.
• Manipulating the Opponent's Deck:

EotE

• Anti-Debuff: Miasmic Crystal lets you ignore Tekeli-Li cards, albeit it has only three charges by default.
• Damage Over Time: "Miasmatic Torment" treachery slowly drains your Partner's health or sanity (on your choice), until you discard it.
• Item Amplifier: Small Radio makes the Partners more useful, as it lets you keep them safely behind and still use their abilities; the Radio itself has limited supplies to trigger its effects, but there are ways to restock them.
• Manipulating the Opponent's Deck:
  • During "Ice and Death" scenario, drawing "Tablet" token makes you discard one card from your deck for each point you fail by (up to 3 on easy/medium, and up to 4 on hard/expert); if you discard a weakness, you have to draw it instead.
  • "Elder Things" set is entirely dedicated to depleting your card supply. "Elder Thing Scavenger" makes you discard top 3 cards of your deck on each attack (drawing any weaknesses), while Guardian Elder Thing makes you discard one card (drawing it if it's a weakness) for each damage you cause to it.
  • "Polar Mirage" treachery from "Silence and Mystery" set gets attached to a location with at least 1 clue; if you find (or take control of) at least one clue there, you'd be forced to discard all but one card from your hand.
  • This campaign introduces new mechanic — Tekeli-li cards, that form a separate deck, and can be shuffled into your deck by various in-game effects; they trigger various nasty penalties when drawn, similarly to normal weaknesses, except they leave your deck after triggering... until you run into them again. Many negative effects you can run into are specifically designed around delivering these cards to you.
    • "Skittering Nonsense" enemy from "Ice and Death" scenario shuffles one Tekeli-li card when you defeat it. If you can't (as the deck run out), it just makes one last ditch attack instead.
    • During "Heart of Madness" scenario, drawing "Plate" token makes you draw a Tekeli-li card; on easy/normal difficulty, it triggers only on a skill failure, while on hard/expert, it's automatic.
    • "Agents of the Unknown" set "punishes" you with Tekeli-li cards if you do (or don't do) certain things: "Primordial Evil" enemy blindly shuffles one card into your deck if you damage it, while "The Madness Within" treachery imposes Willpower test on you, and shuffles up to 4 cards if you fail (or causes horror if it's impossible).
    • "Creatures in the Ice" set actively tries to put more cards into your deck. "Manifestation of Madness" enemy shuffles 2 random cards into your deck whenever it attacks, while "Glacial Phantasm" passively supplies every player in its or connected locations with Tekeli-li cards every round, unless it's exhausted. The only treachery in the set, "Kindred Mist", doesn't add any extra cards, but instead makes you trigger anything you draw immediately, and then put on the bottom of your deck, instead of shuffling them back into Tekeli-li deck.
    • "Nameless Horrors" set not just gives you more Tekeli-li cards, but also makes them more impactful. "Blasphemous Visions" treachery gives you one card right away, and then makes you trigger effects of any that you reveal twice; "Glimpse the Unspeakable" makes you draw and immediately resolve effect of a Tekeli-li card, then shuffles it into your deck (so it can hurt you again later); and "Nightmarish Vapors" gives you a choice between blindly shuffling two Tekeli-li cards and get hurt later, or lose 2 actions and get hurt now.
    • "Forgotten Shoggoth" enemy makes you draw 1 Tekeli-li card when it engages you, while "Rampaging Shoggoth" (both from same set, "Shoggoths") causes two damage to everyone, friend or for alike (excluding other Shoggoths) at its location at the end of every enemy phase, also causing attacked investigators to draw 1 Tekeli-li card.
• Power Nullifier:
  • During "Ice and Death", Terror of the Stars disables your ability to resign of rind clues for as long as it's not exhausted, while during "City of the Elder Things", it prevents you from obtaining and spending keys.
  • "Antarctic Wind" treachery gets attached to location, and for the rest of the round, renders everyone there unable to draw or play cards.
  • "Miasmatic Torment" treachery makes the Partners following you unable to ready (so if you use them once, they stay disabled). It has built-in mechanic to discard it, which should be done quickly, as it also has built-in Damage Over Time effect.
• Status Buff: Mineral Specimen story asset not only lets you investigate with basic Intellect of 6 (and find extra clue), but also lets you disregard Frost tokens (two tokens revealed in one test equals to automatic failure).

TSK

• Bears Are Bad News: During "On Thin Ice", amongst other things, you have to deal with a Ravenous Grizzly, who relentlessly pursuits you while you're in Wilderness locations. The bear has above-average stats, and deals lots of damage.
• Continuity Nod: Flavour text for "Touch of the Beyond" treachery references Virgil Gray, major story character from The Dream Eaters campaign.
• Colour-Coded for Your Convenience:
  • Flavour text for the Keys assigns them colour codes, corresponding to their estimated threat level: green (relatively safe), yellow (moderate threat) and red (extremely dangerous). It's not just for flavour: higher-threat Keys tend to have more lethal effects when unstable (direct damage/horror, Doom straight to agenda, etc).
• Deck Clogger: "Foundation Intel" is a story weakness that does literally nothing — it just gets stuck in your hand, with no option to remove it by any means. However, delivering it to designated location lets you get rid of it, and rewards with experience points.
• Draw Aggro: Coterie Provocateur (from "Dogs of War" scenario), while ready, makes investigators at his location unable to attack any other enemies but him.
• Draw Extra Cards:
  • Ece Şahin lets any investigator to look the top card of their deck, and, if it's not weakness, put it below Ece's card (up to 5 cards). When any Key gets shifted, each investigator draws their cards that were put below Ece.
  • Strangely, some treacheries actually let you to reclaim the hollowed cards, if certain conditions are fulfilled:
    • Passing Willpower test on the "Secrets Lost" treachery with good enough result lets you draw one of your "hollows", if you're willing to take 1 horror.
    • "Matter Inversion" treachery gets attached to an Outsider enemy, boosting it. If you manage to evade that enemy, however, not only that treachery gets discarded (nullifying its effect), but you can also reclaim 1 of your "hollows".
• Encounter Bait: "The Eye of Ravens" requires drawing an encounter card before it can be shifted back to stable side.
• Eye Scream: The Eye of Ravens was originally discovered in an eye socket of a dead Coterie member, meaning that whoever it was, they had it replacing their normal eye.
• The Famine: Amaranth's actions led citizens of Marrakesh suffering from massive famine, as she poisoned all crops with blight. Those who risked to eat the crops anyway, died even faster than those who chose to starve, as they were poisonous. One of scenario-specific treacheries in "Dead Heat" scenario, "Famine", references it as justification for its effect (making investigators starve for resources, by upping price of playing any cards).
• I Just Shot Marvin in the Face: In "On Thin Ice" scenario, visiting "Hunter's Lodge" location for the first time can get you shot by a trigger-happy hunter, unless you manage to calm him down. As he becomes actually helpful afterwards (shooting Monster-type enemies who try to enter), it gets clear that he simply panicked, likely mistaking you for an Outsider.
  And here you thought the Outsiders were the dangerous ones.
• Manipulating the Opponent's Deck:
  • During "Dead Heat", drawing "Elder Sign" token makes you discard 1 card from hand (of your choice on easy/normal difficulty, and random one on hard/expert).
  • "Light of Pharos" Key, when in unstable state, makes everyone discard 2 random non-weakness cards from hand when shifted.
  • "Excruciate" treachery (from "Shades of Suffering" scenario) makes you pass a Willpower test, and then discard several cards, with severity matching the scale of your failure (up to and including discarding your entire hand)... or take 2 damage.
  • "Pinch in Reality" treachery (from "Strange Happenings" set) forces you to choose between discarding half your hand (you have to pick what to discard, and no, you can't discard weaknesses), or spending 1 clue — and it's a question what's worse.
  • "Hollow" mechanic can result in some cards being "hollowed" and set aside for the rest of scenario (though some effects can return them); it's nearly universally associated with the Outsiders. Many cards and effects actively use it for their payload:
    • Four scenarios that actively feature Outsiders as your enemies, "Dancing Mad", "On Thin Ice", "Without a Trace" and "Congress of Keys", gradually hollow players' cards as agenda deck advances (except for "Congress of Keys"), and have certain tokens' effects hollowing your card when drawn (except for "Dancing Mad"). Additionally, they feature unique scenario-specific enemies that do the same.
    • "Sable Glass" Key, when in unstable state, hollows the most expensive card in each player's hand; unfortunately, it's the only way to shift it back to stable side.
    • "Outsiders" set is all about this mechanic. "Paracasual Entity" enemy hollows top card of your deck when it engages you; "Apocalyptic Presage" enemy hollows either top card in the deck or asset under control of every player when it enters play (you can defeat it it to regain up to 3 cards, but that would prevent you from adding it into victory display); and "Substance Dissimulation" treachery either hollows 1 card in your hand or asset under your control, or, if you have the copies of already hollowed card in hand or play, forces to discard these cards instead and take 1 damage and horror for each.
    • "Secret War" set gives the player some chance to protect against hollowing, but also has potential to be even more destructive. "Memory Variant" sticks around and hollows any events you play, until you pass Willpower test to get rid of it, while "Secrets Lost" is a one-time effect, that can hollow up to 3 cards if you fail Willpower test.
    • "Paradigm Effacer" enemy (from the "Agents of the Outside" set) passively drains your deck, hollowing the top card of your deck (unless it's a weakness) each time you end your turn at its location.
    • "Warped Reality" treachery (from "Spatial Anomaly" set) gets attached to a location, and hollow 1 of the cards from your hand (excluding weaknesses) each time you end your turn there. It can be discarded, but it requires spending two actions (with you likely already spending at least one to enter, unless it spawned on top of you).
• Mook Maker: Protoplasmic Reassembler enemy from "Without a Trace" scenario keeps taking away cards from the decks of investigators at its location, and making them into "Golems", who then attack the investigators (at least, they're weak); no, killing them don't give you cards back: they gets "hollowed" instead.
• Power Nullifier:
  • "Calling Card", a treachery from "Sanguine Shadows" scenario, gets attached to a location and makes investigators unable to spend clues (anywhere) until they get rid of it, which shuts down most special abilities on locations.
  • In "Without a Trace" scenario, Void Chimera's true form makes you unable to expose concealed mini-cards for as long as one of its other forms is still in play.
  • Coterie Envoy enemy disables your ability to expose concealed mini-cards at his location. And he's actively trying to get into such locations.
• Reduced Mana Cost: Inverted with "Famine" treachery (from "Dead Heat" scenario), that increases the resource cost to play any card by 1 till the end of the round.
• Status Buff: The Eye of Ravens lets investigator to set basic value of one of their stats to 6 (no investigator has above 5 by default) for duration of one skill test.
• Zombie Apocalypse: In "Dead Heat", most of your enemies are various undead minions resurrected by Amaranth's magic, including actual zombies, who're slaughtering the civilian population. If you fail to stop Amaranth, the undead would murder and devour the remaining civilians.

FaHV

---

YMMV

---

Goddamned Bats

Core game

• The "Rotten Remains" treachery from the "Striking Fear" set. It tests Willpower, and deals horror if investigator fails, proportionally to how hard they fail it; Rogues suffers the most, generally having poor Willpower and limited number of options to boost it. Having three copies in the deck, and coming from one of the most recurring set in the game, it would come to cause you problems time and time again. It also has a twin brother, "Grasping Hands" from the "Ghouls" set, which tests Agility and deals damage, but it's way less common and thus less infamous.
• The "Frozen in Fear" treachery from the "Striking Fear" set forces investigator to waste (limited) actions on even the most basic tasks, which, in turn, would slow down their progress so much, they likely wouldn't make it in time; the only way to discard it is to pass Willpower test, which may be problematic when playing as Rogue. Whenever it comes to deciding what to cancel, this card is amongst the top priority ones, alongside "Ancient Evils".
• The "Crypt Chill" treachery from the "Chilling Cold" set forces the investigator to pass hard Willpower test or discard one asset from play (or losing health if it's impossible). The test is hard enough that some investigators wouldn't be able to reliably pass it.
• Acolyte from "Dark Cult" set; not only it spawns with 1 Doom on it, but it spawns in an empty location, meaning that you have to go out of your way to get that time back. There are enough of them in the deck to show up time and time again, and it's one of the sets which would show up in nearly every campaign at least once. It isn't very strong on its own, but frequently shows with the other cards which can add more Doom to it.
• Hunting Nightgaunt enemy has only one notable ability — it doubles negative modifiers on every chaos token you draw when trying to evade it, which often makes doing so borderline impossible (especially since it has the "Hunter" keyword, which makes it actively pursuing investigators).
• "The Yellow Sign" treachery from the "Agents of Hastur" set has hard enough Willpower test that investigators can reliably fail to pass it and suffer horror, but the more annoying effect is that it can force investigator to draw a weakness with "Madness" trait from their deck; if the player doesn't have such cards, it's a freebie, but if they do, it can screw them over, as the list of such cards includes some very nasty ones (and for some investigators, it's a part of their signatures).
• The "Dreams of R'lyeh" treachery from the "Agents of Cthulhu" set reduces investigator's Willpower and Sanity, until they deal with this card. The problem is, to discard that card, you have to pass Willpower test, while suffering from the stats reduction effect. And penalty to Sanity is very painful for any investigator who has low stat to begin with.
• The Locked Door treachery spawns on whichever location has the most clues and prevents it from being investigated until an investigator passes a moderately difficult skill test of 4 fight (to break the door) or 4 agility (to pick the lock). Your clue gatherers will likely struggle to pass this test without assistance, and if this happens on a location critical to the scenario (e.g. the only one with clues left) this can seriously slow the team down and potentially cost them the scenario.

The Dunwich Legacy campaign

• The Conglomeration of Spheres enemy from the "Hideous Abominations" set lacks offensive capabilities, but has more health than some investigators, and forces investigator to discard any Melee cards used against it — while non-Melee cards usually have limited ammo or charges. It would struggle to actually kill you, but would try to slow you down; it always shows up in scenarios where you're pressured to reach some place quickly.
• "Claws of Steam" treachery from "The Essex Express" scenario forces to pass a Willpower test; on a failure, it not only does damage (tolerable), but also makes investigator unable to move for entire round... in scenario with Advancing Wall of Doom. There's also the "Broken Rails" treachery, which makes investigators lose 1 action, thus slowing down whatever task you're trying to perform.
• "Collapsing Reality" treachery in the "Lost in Time and Space" scenario not only causes damage (and horror, due to scenario-specific rules), but discards your location and drops you in the very beginning. Have fun spending several more turns going back to where you were before this card hit you.

The Path to Carcosa campaign

• Roach Swarm enemy from "Decay and Filth" set exists to annoy clue-searchers; they're just hard enough to evade to require some card investment, and have their combat scaling with location's shroud, making it hard to swap them. If investigator tries to investigate with them still being nearby, they would be just hit by attacks of opportunity, which, while does only 1 point of damage, still slowly wears down your protection (or your health).
• "Corrosion" treachery from "Decay and Filth" set exists to harass any investigators who relies on key assets, as it makes them discard multiple assets at once, with severity scaling with shroud. Its counterpart from Return to the Path to Carcosa instead targets investigators relying on events.
• "Delusions" set rarely poses real threat, but it's very annoying, due to putting various restrictions on the player and only being discardable by wasting almost all your actions. The one card which doesn't do that, "Descent into Madness", instead makes investigator losing actions if they have enough horror, which they usually have, given this campaign's focus.
• "Straitjacket" treachery from "The Unspeakable Oath" scenario, once drawn, forces investigator to wear it (taking both hands and a body slots), and can't be removed except by spending two actions. It may outright put investigator out of action for some time.
• "A Shadow Behind You" treachery from "The Pallid Mask" scenario forces investigator to waste one action every turn (out of three), or discard either all resources or all cards from hand to get rid of it (potentially putting the investigator out of action for a turn or two).
• "Realm of Madness" treachery from "Dim Carcosa" scenario forces you to discard your cards; its unique gimmick is that effect scales with amount of horror on your investigator, so it can discard half your hand, or more (especially since in this scenario, you can keep accumulating horror past your usual maximum).

The Forgotten Age campaign

• Two treacheries exists solely to pin you to place:
  • "Entombed" treachery (from "Deadly Traps" set) makes investigator stuck in one place and waste actions to get rid of it. And test difficulty is just hard enough to potentially require more than one attempt.
  • "Lost in the Wild" gives a chance to avoid it, but if it actually lands, you're stuck at your location until the end of your turn.
• "Serpents" set isn't hard to deal with, but it's a trap: any "easy" ways out cause you either vengeance points or Poison, both of which would have severe long-terms harmful effects:
  • Pit Viper enemy is very easy to kill, but doing so costs vengeance points. If you decide to deal with it non-lethally, any mistake can result in you ending up poisoned.
  • Boa Constrictor enemy has low damage output, but is hard to kill itself, and can prevent you from readying your assets (making it much harder to deal with it if you failed to dispatch it quickly). If you still kill it, you get the whopping two vengeance points. You can try to avoid it, but it wouldn't avoid you, being a "Hunter" enemy.
  • "Snake Bite" treachery from the "Serpents" set forces to choose between essentially One-Hit Kill for an Ally under your control, or direct damage to investigator themselves (with an extra "bonus" in the form of Poison).
• "Lost in Time" treachery from the "Temporal Flux" set forces investigator to pick and shuffle non-story asset under their control back to the deck, without any saving throws; if that asset had any damage or horror on it, those gets dealt to investigator instead. And if you have nothing, it targets your hand instead, discarding 3 cards. No matter what, it would screw you over.
• Fang of Yig enemy (from "Yig's Venom" set) prevents poisoned investigators from playing cards or committing them to skill tests, essentially crippling them without actually doing anything to kill them. They don't pose much danger to non-poisoned investigators, however.
• "Timeline Destabilization" treachery from "The Boundaries Beyond" scenario aims to disrupt your progress. If drawn, it enforces the Willpower test (which scales with the number of discovered locations), and if the player fails to pass it, it goes into exploration deck, so, instead of a new location you want to find, you can accidentally draw this one, wasting that exploration. It also deals minor damage and horror.
• "The Heart of Elders" scenario has several scenario-specific threats, all of which aims to slow you down:
  • "Poisonous Spores" treachery poisons everyone who doesn't move away from its location before the end of the round. Those already poisoned instead suffers horror. Either run around instead of doing your task, or get poisoned and suffer even more later on; make your choice.
  • Apex Strangleweed enemy has more health than some investigators, and though it lacks offensive capabilities, each time it makes attacks of opportunity, it takes away all investigator's actions and forces them the end their turn immediately. It can be disabled by one of the possible supplies (a pocketknife), but players are so limited in picking those, it's entirely possible that no one would bother to take it.
  • "Ants!" treachery imposes hard Agility test, and on a failure, makes you discard cards from hand (at random) and/or cards you control; with the difficulty of 4, and severity of effect scaling with how badly you fail, even one card can leave you defenceless, and there are multiple copies of it.
• "Wracked in Time" treachery from the "Shattered Aeons" scenario is yet another "fail a test, suffer damage" card... except for the fact that any asset which gets damaged by it, unless it's defeated, must be then shuffled back into your deck, making it harder to stay well-equipped while also avoiding losing too much health.

The Circle Undone campaign

• "Centuries of Secrets" treachery from the "City of Sins" set, if investigator is particularly unlucky, can severely hurt investigators who rely on key Allies, by dealing direct horror to each of them. It also deals direct horror to investigator themselves.
• "Realm of Torment" treachery from the "Realm of Death" set makes investigator trigger every "Haunted" effect in their location at the start of their turn, with all the chaos that follows. It can be discarded by passing Willpower test, but it must be done after gaining it, with failed attempt also triggering the "Haunted" effects.
• "Witchcraft" set consists of the treacheries dedicated to make life harder, without actually ending it, be it through targeting your assets ("Bedeviled"), your hand ("Diabolic Voices") or your stats ("Wracked").
• Vengeful Witch enemy from "The Wages of Sin" scenario is tough enough to often warrant using extra cards to kill, but the worst part comes when she dies, as she deals direct damage and horror to all investigators around her, which you can't soak with your assets. Attempt to evade her would only make her continuously pursuit you, being a "Hunter" enemy.

The Dream Eaters campaign

• Swarm enemies in general are nasty; with few exceptions, they're weak (with or without "swarm" cards), but the "swarm" cards they use are taken from investigators' decks, making killing them an urgency, as they can take something valuable this way. It also makes it harder to kill them, as each "swarm" card allows to absorb some damage while dealing more damage/horror. Some of them also combines it with extra effects which makes them even more annoying:
  • From the "Zoogs" set:
    • Inconspicuous Zoog enemy combines "swarm" mechanic (with higher value than other zoogs) with inability to kill it in one attack, no matter what, as it cancels any excessive damage which would otherwise target the other swarm cards or the host, and runs away to a connected location. And even if it gets killed, it can respawn thanks to "Zoog Burrow" treachery.
    • "Zoog Burrow" treachery can add even more "swarm" cards to any zoog in play, or, if there's none, just outright spawn one from either the encounter deck or discard pile. You just barely killed the Inconspicuous Zoog after multiple turns? Too bad, it's here again.
  • Ancient Zoog (from "Beyond the Gates of Sleep" scenario) lacks its own "swarm" cards; instead, it just hides somewhere, and keeps adding more and more "swarm" cards to every other zoog, until you find and kill it. It's Elite, which makes it immune to many cards which would otherwise allow to quickly deal with it.
  • Cats from Saturn enemy (from "Dark Side of the Moon" scenario) increases their "swarm" value as alert level goes higher, making dispatching them take longer than you can afford. Fortunately, every time they move or get evaded, they lose their "swarm" cards one by one.
• "Will of the Spider Mother" treachery (from the "Agents of Atlach-Nacha" set) forces investigator to pass a Willpower test; the test becomes harder, due to inability to commit cards, if there're any Spider enemies in your location (and this card shows up in the situations where all your enemies are spiders), and if you fail it, you can't investigate or fight until the end of the round — while still having to deal with the spiders in your location and being on a time limit.
• "Law of 'Ygiroth" pack of treacheries (from the "Agents of Nyarlathothep" set) not only puts restrictions on what the player can or can't do, but also makes it in such a way that just checking the conditions becomes annoying task (like "you can't play the cards with odd number of words in the title"). And they're "hidden", meaning that they would occupy your (limited) hand until you perform (equally awkward) condition to discard them.
• "Deeper Slumber" treachery (from the "Dreamer's Curse" set) drastically reduces hand size, and forces to check it (discarding excessive cards) any time you draw anything, making it impossible to plan anything ahead.
• "Prismatic Phenomenon" treachery (from the "Dreamlands" set) forces you to spend extra action the first time you gain resource, or draw/play card, every round, making you unable to use your actions efficiently. To add insult into injury, the only way to get rid of it is to successfully investigate a location, which some investigators may be simply not equipped for (not to mention, being weakened by this card's effects).
• "Night Terror" treachery (from the "Merging Realities" set) goes into your threat area, and hits you each time you fail any test (which can be very painful for Survivors, who often make it core part of their gameplay), by forcing to reveal 3 cards from your deck; each weaknesses immediately gets drawn, while any other cards gets outright removed from the game (neutering their ability to reclaim these cards). You have to pass a Willpower test to remove it, which you also can fail (though, fortunately, the card gets removed regardless).
• "Song of the Magah Bird" and "Wondrous Land" treacheries (both from "The Search for Kadath" scenario) aim to slow down the investigation (in scenario with very strict time limit, and harsh long-terms consequences if you lose), on the threat of increasing Doom; first one locks you in location unless you pass a hard test, the second one can make you unable to investigate a location unless you're willing to get punished for it.
• "Endless Descent" treachery (from "A Thousand Shapes of Horror" scenario) puts the top-most location on the bottom, essentially prolonging your descent — while you're against the timer and pursued by Advancing Boss of Doom.
• From "Where the Gods Dwell" scenario:
  • "Restless Journey" pack of treacheries tries to combine all the most annoying qualities in one cocktail. They makes you unable to commit more than one card to skill tests each round (seriously hurting your effectiveness), they're "hidden" (meaning that they take up limited place in your hand), and can only be discarded through skill test (each version tests different stat), failing which would also increase Doom. They also have the "peril" keyword, so your friends wouldn't help you. And if all that wasn't enough, there's a Crawling Chaos lurking around which goes more and more dangerous the more "hidden" cards you accumulate, these ones included.
  • "Abandoned by the Gods" treachery makes you pass a Willpower test, and, on a failure, discard cards from hand with with specific cost. What makes it particularly annoying is that your failure would hit not just you, but entire team (and it having "Peril" makes said team unable to back you up).
• "Caught in the Web" treachery (from the "Weaver of the Cosmos" scenario) not only lowers your Agility, but also limits you to only one movement action per turn — in scenario where actively moving around is crucial for success, and where even main boss is actively trying to escape from you.

The Innsmouth Conspiracy campaign

• Initiate of Dagon and Priest of Dagon (both from the "Agents of Dagon" set) are another take at Doom-generating cultists, but with their own annoying gimmick: both spawns without Doom by default (only getting it later), but Initiate gains massive boost to Fight and Evade until she gets that Doom, and Priest outright can't be defeated till then; so even if they drop right on your head, you have to wait for at least a turn before dealing with them.
• "Agents of Hydra" set aims to drain investigators' hand, with painful extra gimmicks:
  • Lloigor enemy keeps pursuing investigators without actually engaging them (due to "Aloof" keyword). While it's nearby, it forces all investigators in its or connected location to discard a random card from hand at every enemy phase. And if they decide to fight it after all, they would meet a very durable enemy with decent Fight, whom they likely wouldn't kill fast enough to avoid being hit by its ability one more time.
• "Psychic Pull" treachery not only forces investigator to discard a random card from their hand, but then also imposes a Willpower test (with the difficulty scaling with discarded card's cost) to avoid losing an action. Both effects are amongst most hated, and this card combines them.
• "Malfunction" treachery from namesake set can randomly break your Vehicle, forcing you to stop and pass a not-trivial Intellect test to fix it. It's not as painful in the "Devil Reef" scenario, which goes at more or less standard pace, but in the "Horror in High Gear", it may either slow you down while you're trying to outrun pursuit, or make you unable to slow down and investigate a road ahead to not run into something nasty.
• "Rising Tide" set of treacheries synergises with flood mechanic. "Undertow" punishes the players for attempts to leave flooded locations with damage and horror (unless they're willing sacrifice their cards to pass a test to get rid of it); "Riptide" takes away your assets; and "Rising Tide" speeds up the flooding process, making other effects related to flooding more dangerous.
• Hunting Deep One enemy (from the "Devil Reef" scenario) can drug you from your boat, and then prevent you from jumping back unless you either kill it or evade it. Additionally, it prevents you from gaining resources, which may be painful when trying to dispatch it. And if you fail to quickly deal with it, you may run into this scenario's nasty pack of treacheries specifically made to grind investigators who think that they can survive without a boat.
• From "Horror in High Gear" scenario:
  • Hybrid Assassin enemy can't hurt investigators much, but as he moves twice if he can't reach the investigators in one move, it's borderline impossible to outrun him — while fighting him wastes time and allows other, nastier enemies to catch up. He also spawns right on top of you, instead of far behind, like most other enemies in this scenario.
  • "Eyes in the Trees" treachery is yet another "pass a test or discard cards" treachery... which scales with your performance, and, if you're a driver, can hit your teammates as well.
• From "A Light in the Fog" scenario:
  • Deep One Hatchling enemy has abysmal stats, but if it's killed, it can and likely would attract attention of another, much stronger Deep One who would come for your blood. But if you stop trying to kill it, it wouldn't stop trying to kill you; and each time it tries to engage you, you have to choose between suffering small amount of horror, or losing an action. To make it even more annoying, it has "Surge" keword, so once it spawns, it immediately gets followed by another card.
  • Deep One Nursemaid enemy just quietly sits in a location, while passively boosting all the other, more dangerous enemies. But if you try to attack it, it would drop another encounter card on you (at least, it loses "surge" effect to not make it nastier than it has to be).
  • "Taken Captive" treachery dumps investigator in the cell, from which they have to escape while also taking back their keys. This is in scenario which puts on strict time limit, and outright kills investigators if they fail to escape in time.
• "Stone Barrier" treachery (from "The Lair of Dagon" scenario) blocks the way out of its location, requiring passing a skill test every time you try to go through, which costs an action to even initiate. Once it spawns, it stays there forever, with no way to get rid of it permanently.
• "Treacherous Depths" treachery (from the "Into a Maelstrom" scenario) forces the player to choose between increasing flood level, or discarding assets from play with their total cost scaling with you location's shroud; so, a choice between flooding a location and getting even less place to breath, or potentially discarding tons of valuable cards, as shroud sometimes can be very high. It has "Peril" keyword, preventing your friends from bailing you out.

Edge of the Earth campaign

• Tekeli-li mechanic as a whole; a deck of various weakness cards which can get shuffled into your deck through a million-and-one ways, and screw you over when you lest expect it, while rarely, if ever, actually pose a danger directly. Enemies and treacheries who can drop such cards on the players are amongst the most annoying to deal with, though some are worse than the others. Some sets exists to either reliably deliver these cards to the players, or make them even more annoying:
  • Primordial Evil enemy (from the "Agents of the Unknown" set) shuffles Tekili-li cards when you attack it; as it has very high health pool, you may clog your deck with multiple Tekeli-li cards before you kill it.
  • "Creatures of the Ice" set is fully dedicated to this mechanic, but only the enemies from it pose any threat. Manifestation of Madness enemy shuffles two Tekeli-li cards on each attack, and actively pursuits investigators (being a "Hunter"), while Glacial Phantasm slowly follows the investigators (aiming at locations with more people) and then forces everyone in its location to shuffle one Tekeli-li card, without giving a chance to avoid it.
  • "Blasphemous Vision" treachery (from the "Nameless Horrors" set), on top of shuffling those cards into your deck, makes you resolve them twice each time you trigger them, until you get rid of it; but the true pain comes when it gets paired with the other cards from same set: "Glimpse the Unthinkable", just before shuffling card into deck, forces you to immediately trigger it, while "Nightmarish Vapors" gives a choice between wasting two actions (you have only three by default) or shuffling two Teki-li cards.
• Every single Elder Thing exists to torture investigators, in one way or another:
  • "Elder Things" set is all about harassing investigators' decks by forcing them to discard cards from it, be it when they attack you (Elder Thing Scavenger) or when you attack them (Guardian Elder Thing); both enemies have just enough health to possibly require more than one turn to deal with, and both are "Hunters", meaning that you can't just run from them and forget.
  • Constricting Elder Thing enemy (from "To the Forbidden Peaks" scenario) gains more health at higher levels, and can prevent an investigator from advancing to the location above, forcing them to spend time on killing it instead of progressing further.
  • Benign Elder Thing enemy (from the "City of the Elder Things" scenario), despite the name, isn't friendly and would attack investigators. It has 1-1-1 statline, making it easy to kill, but it spawns with Doom on it, and, if killed, adds that Doom directly to the current Agenda. What you're supposed to do with it is to pass a Willpower test to remove it from the game permanently, but you have to either spend two actions to engage and evade it, or just tank its attack of opportunity. Another issue with it is that shoggoths attack them on sight, with the same results as if it was done by you.
• "Left Behind" set consists of two enemies who spawns with Doom on them. They're easy to kill... but it's actually the worst thing you can do, as it only makes their Doom tokens to move to their location instead (from where it can't be removed). Instead, you're supposed to deal with them through specific non-lethal means, which would make them despawn... while they're trying to kill you. The set also includes a treachery which makes dealing with them even harder while putting on them additional Doom.
• "Miasmic Torment" treachery (from "Miasma" set) attaches to your partner, and disables them, making them unable to get ready, and dealing either damage or horror to them once your turn ends. You can remove it, but it costs an action and requires a skill test. This thing can be quite annoying when you just can't afford to waste time.
• Giant Albino Penguin isn't aggressive by default, but makes you waste more actions each time you try to move from or into its location (it's "Aloof", and thus wouldn't attack first). Grew tired of it and decided to kill it? But you would lose an action just to engage it, and then you have to kill an enemy with 3 health. In short, no matter what you do, the penguins would slow you down. And then there's "Wuk! Wuk! Wuk!" treachery, which either moves that penguin to you, or puts Doom on it (and when there's no penguins, it drops one right on top of you).
• "Polar Mirage" treachery (from the "Silence and Mystery" set) flat-out discards all non-weakness cards from your hand if you try to discover clues in location to which it gets attached (and you have very little control over where it spawns). It can and would ruin your plan of action if drawn in the wrong moment. At least, it discards once it hits.
• "Hanging on the Edge" treachery (from "To the Forbidden Peaks" scenario) can deal you damage and drag you to a location below, while any Expedition assets stays above and must be recovered. "Avalanche" treachery from the same scenario is even worse, as it drags you immediately, and only then puts a skill test to avoid being dragged even further. This card can easily undo several turns of progress.

The Scarlet Keys campaign

• Pretty much entire "Hollow" mechanic exists to annoy the players and slow them down (by temporarily removing their cards from the game), but some enemies exists solely to make it more annoying:
  • Paracausal Entity (from "Outsiders" set) is a "Hunter" enemy "hollows" a card belonging to investigator every time it engages them. It's relatively easy to kill, but would show up again and again (as there're multiple of them), while "hollowed" card would be missed for a while even after the enemy gets defeated.
  • Paradigm Effacer (from "Agents of the Outside" set) is both a "Hunter" (so it keeps pursuing investigators) and "Aloof" (so it doesn't attack on its own, and you have to engage it first, spending action). Just ending your turn in the same location is enough to lose a card as "hollow"; and it would persist and keep doing its dirty deed until killed or otherwise got rid of.
  • "Secret War" set exists to make the players lose their cards as "hollows" in huge quantities:
    • "Secrets Lost" forces the player to pass a non-trivial Willpower test, and punishes the failure with losing up to three cards as "hollows".
    • "Memory Variant" forces you to set aside as "hollow" any event card you play. It may be discarded by passing a Willpower test of above-average difficulty.
• Concealed mechanic. Concealed enemies goes "into shadows", leaving several mini-cards you have to uncover before you can kill them, with some of those being decoys. Most of such enemies are weak and easy to kill (once revealed), but often comes with the ways to make the search itself painful, and almost any enemy "in the shadows" has some way to harass the players without directly engaging them. In addition, some sets are made specifically to make already concealed enemies more annoying.
  • "Crimson Conspiracy" set is another take on annoying Doom-generating cultists, with new gimmick:
    • Coterie Agent enemy not only hides in some remote corners (just like Acolyte), but also sets around several decoys, so you may take several turns to even find in which corner they hide.
    • "Conspiracy in Red" treachery puts more Doom on enemies in shadows (including Coterie Agents), making the hunt even more of an urgency. No concealed enemies? It just spawns new one.
  • "Figures in the Dark" treachery (from "Dark Veiling") set either makes every enemy in shadows attack you (can be very painful if there're enough of them), or makes every investigator lose an action (wasting precious time). It usually can't cause your defeat by itself, but it certainly makes life harder for everyone. And "Peril" keyword makes it harder to counter.
  • Coterie Envoy (from the "Mysteries Abound" set) prevents any concealed cards in its location from being exposed while it's alive; and as it's also "Aloof", you have to waste an action to engage it before you can deal with it. Not very threatening on its own, it slows down your efforts to get rid of other, more dangerous enemies.
  • "Knives in the Dark" treachery (from "Shadow of a Doubt" set) deals 2 damage when you expose a decoy. Tolerable at first, it can quickly stockpile if there're many Concealed mini-cards, making you run out of damage soak options.
• "Scarlet Sorcery" set exists to make "Elite" Coterie members (read: Mini-Boss foes like the Beast or Amaranth) more dangerous and annoying, but can't kill the players on its own.
  • "Bound in Red" treachery increases all stats of the Coterie enemy with highest printed health (which is nearly always the already-dangerous main villain of scenario). Higher stats means more resources, cards and time wasted. And only way to remove it without a fight is by shifting a Key to unstable side, which is painful by itself, and requires having a Key in the first place.
  • "Key Charge" makes each Coterie member shift their Keys, which comes with various nasty effects, and then it "surges" into other card. Specific danger varies from Key to Key, as some effects are nastier than the others.
• "Spreading Corruption" set exists to slow down the players, in the game where you're always on a time limit:
  • "Compulsion" treachery randomly triggers at beginning of your turn (you draw a chaos token to determine it), forcing you to waste two (out of three) actions to discard it (even if it would provoke attack of opportunity).
  • "Distorted Reasoning" treachery makes investigator unable to perform same action twice in a row (which can severely hinder any specialists, like dedicated clue-searchers or dedicated fighter). It can be discarded at the end of the turn, but it requires passing a Willpower test; good luck doing it as Rogue.
  • "Touch of the Beyond" treachery puts Doom on your asset with highest printed cost, forcing you to either tolerate having 1 less turn to do your objective, or get rid of asset in question (with only Mystics being able to remove the Doom itself).
• "Strange Happenings" set:
  • "Heavy Rain" treachery puts investigator through Willpower test, and if they fail, either makes them take up to 3 horror (similarly to infamous "Rotten Remains"), or drop up to 3 clues in their location (forcing to spend time on recovering them).
  • "Pinch in Reality" treachery either discards half of your hand, or forces you to spend 1 Clue (not even discard; spending means it's gone); both effects would slow you down, albeit are still possible to recover from. For extra annoyance, it has "Peril" keyword, so no outside help.
• "Dead Heat" scenario has "Cornered!" treachery, which forces you to pass Willpower test; if you fail, you have to suffer horror, unless you're willing to let a civilian at your location die (letting too many to die leads to severe penalties).
• "Dealings in the Dark" scenario eventually turns into big tug-of-war — and there are bunch of cards which are dedicated to putting Doom on cultists, giving them immediate advantage:
  • "Shadowed" and "Accosted" treacheries, on top of extra Doom, forces investigator to pass a Willpower/Agility tests to avoid suffering horror/damage, respectively.
  • "Light Out of Void" treachery gives a choice between adding Doom on Cultist enemy with highest Evade, and suffering 1 damage and 1 horror; it has "Peril", so your friends can't bail you out.
  • Umbral Harbinger enemy is relatively weak, but has 5 Health (though, if killed, it stays dead). What makes it nasty is the fact that anytime it gets damaged, a point of Doom gets put on a Cultist. You can just keep avoiding it, as it has only 1 Evade, but as a "Hunter", it would keep pursuing you.
• "Scarlet Shadows" scenario:
  • "Calling Card" treachery disables spending clues (stalling progress) until a location to which it gets attached gets successfully investigated with at least 2 successes.
  • Bound Nightgaunt enemy is a twin brother of Hunting Nightgaunt from the Core game (which is also present in this scenario). It mirrors the Hunting Nightgaunt, dealing horror instead of damage, and doubles negative modifiers on tokens drawn when attacking it; this can make investigators who're not well-prepared to fight it consider just running away from it, even if it has a non-trivial Evade rating.
• "Shades of Suffering" scenario has "Spirit Harvest" treachery, which forces investigator into Sadistic Choice between everyone suffering 1 damage and 1 horror (which can quickly stockpile, as there's more than one such card in the deck), and Tzu San Niang shifting her key (causing all investigators to lose an action, thus risking running out of time).

The Feast of Hemlock Vale

• Depending on the current day, there would be a certain treachery presented in every scenario you play; day one treachery is tame, but the other two may be quite annoying:
  • "Downpour" treachery (present in every day two scenario) can cause investigator to lose some or all of their actions, or their clues, unless they pass an Intellect test. It has no means to kill you, but can severely slow you down, so something else would; Guardians take it worst, having few means to either pass the test, or mitigate the impact.
  • "Otherworldly Vision" treachery (present in every day three scenario) works just like a "Rotting Remains" (fail a test, take some horror, scaling with severity), but with a catch: if there are any Colour enemy at your location, the test's difficulty goes to 5, and with it, the potential impact. To prevent it from being too lethal (as for some investigators, it's sure death), you're given the option to replace any amount of horror with discarding random cards from hand, which is still annoying, but not immediately fatal.
• "The Forest" set exists mainly to harass the players, with little actual killing power (made worse by it being used in scenarios which punish excessive movement):
  • Cochleal Stag is tough, but not aggressive; its main danger comes not from its fighting prowess, however, but from the fact that its mere presence nearby drops everyone's skills during Mythos phase, making everyone more vulnerable to treacheries. At night, it also becomes Elusive, meaning that it would actively try to escape from you (on top of it already being Aloof by default).
  • Forest Watcher spawns with Doom on it (reducing your time while it stays alive), and hides at some empty location. What makes it more annoying than Acolyte (whose template it uses) is that it's Aloof (and, at night, Elusive), meaning that you have to spend precious action to just engage it... and then, if you fail to kill it in one go, it would escape.
• "Myconids" set:
  • Black Amanita (from "Myconids" set) is a poisonous mushroom that just sticks in some location and causes direct horror to everyone finding clues at its or connected location (unless it's exhausted); it's not hard to deal with, but can be a serious annoyance to clue-searchers if it drops at some crucial area, or somewhere it can't be reliably killed.
  • Corpse Lichen (from "Myconids" set) is durable enough to take some time to kill, which is made worse by it regenerating after every attack. And it can't be just run from, as it's a Hunter (meaning it actively pursuits you). It barely deals any damage, but if you decide to just ignore it, it would slowly chew on your health and sanity.
• "Agents of the Colour" set:
  • Miasmatic Shadow (from "Agents of the Colour" set) is invulnerable to anything but Spells, Relics and Science cards, but otherwise deal very little damage and horror. It isn't aggressive by default, but if ignored, would immediately attack once you discard anything at its location (and can do so unlimited amount of times), which can make it a huge annoyance for investigators who're likely to provoke them, yet unlikely to dispatch them on their own due to simply lacking the required cards.
  • "Alien Whispers" treachery (from "Agents of the Colour" set) poses little danger to investigators themselves, but can quickly drain their assets, or, worse, the residents accompanying them.
• "Calcification" treachery (from "Horrors in the Rock" set) causes direct damage the first time you move each round; it can be defused before it hits you, but can be annoying to some investigators, who may not be able to pass the Combat test to get rid of it, forcing them to take damage anyway to discard it automatically. It reaches its peak power during "Written in Rock" scenario, where you're not exactly in control of your movement.
• Stalking Hybrid (from "Twisted Hollow" scenario), true to its name, pursuits investigator bearing the lamp, and makes them drop it, slowing down the entire group. It starts relatively easy to kill, having only 1 health, but grows tougher and tougher as darkness level increases, potentially making it impossible to kill before it makes you drop the lantern.

---

Demonic Spiders

• From the core game:
  • The "Ancient Evils" treachery has just one effect — it places one Doom on the agenda, effectively leaving the investigators with three fewer actions each to finish the scenario. Additionally, it is one of the few Doom-placing effects that can advance the agenda right on the spot as opposed to waiting until the start of the mythos phase. Cards that follow the "Ancient Evils" template in other campaigns (or otherwise fulfill a similar function) are generally just as nasty as the original, and just as loathed.
  • The "Wizard of the Order" enemy from the "Dark Cult" set is like the Acolyte, but instead of entering play with 1 Doom, it generates 1 Doom at the end of the mythos phase of every turn. It spawns at an empty location, and if left alone, it can cost the investigators the game.
• In The Dunwich Legacy campaign, the "Beyond the Veil" treachery (from the recurring "Sorcery" set) is put into play in an investigator's threat area, but does nothing... until their deck runs out of cards, at which point it deals them ten points of damage - enough to One-Hit KO most investigators, as even the tougher ones only have 9 health at most. And there are plenty of effects in The Dunwich Legacy campaign that discard cards from investigators' decks directly, with one such card also being in the "Sorcery" set.
• The Path to Carcosa campaign:
  • The "Seeker of Carcosa" enemy (from the "Echoes of the Past" scenario) sucks out clues in its location, and once they run out (which happens quickly, as there are the enemies who do the same), starts accumulating Doom. With three of these fellas being in the deck, they can end the scenario very quickly.
  • From "Dim Carcosa" scenario:
    • The "Dismal Curse" treachery starts with a test difficulty of 3 and deals 2 horror on a fail, but gets +2 to both for investigators who've suffered too much horror, making it both hard to avoid and hitting like a truck.
  • "The Final Act" treachery works exactly like "Ancient Evils", but has doubled effect (taking away two full turns in one shot), and immediately "surges" into another encounter card.
• The Forgotten Age campaign:
  • From "The Forgotten Ruins" set:
    • "Ill Omen" treachery is like "Ancient Evils", but worse. It puts the Doom tokens on locations, where it stays even if Agenda advances, so the more Agendas scenario has, the more time in total it chops each time it hits. It also has "Peril" keyword, preventing the other players from assisting in dispatching it. And as a tip on the cake, there are many locations with additional penalties if there's Doom in them.
    • "Ancestral Fear" treachery forces the players into a Sadistic Choice: either it adds Doom to a location (similarly to "Ill Omen" from same set), permanently taking away some time, or rises Vengeance (albeit this at least removes it from the game), which would hurt the players even after scenario is finished. It has both "Peril" and "Surge" keywords, meaning that it's hard to cancel and it would be immediately followed by another encounter card.
  • "Conspiracy of Blood" treachery (from "The Threads of Fate" scenario) lowers Doom threshold of the current Agenda (and can stuck up to two times), which can screw you over if something else rise Doom. It can be disabled after triggering, but it requires going out of you way, and imposes Willpower test which makes things worse if failed.
  • "Window to Another Time" treachery (from "The Boundaries Beyond" scenario) is another Sadistic Choice card; either it hits like "Ancient Evils" and takes away your precious time, or it shuffles "Ancient" location back into exploration deck, possibly undoing several turns of your hard work, without any guarantee that you would be able to catch up. To add insult into injury, "Peril" keyword prevents teammates from assisting you.
  • "Lost Humanity" treachery (from "The City of Archives" scenario) forces you to pass a hard Willpower test, and removes your cards from the game if you fail, with effect scaling with your performance. It's very nasty effect in the best of times, but here, you're stuck with low stats, without many of your powerful cards, scenario's goal is to gather cards in hand, and it can drive you insane if it reduces you below certain amount of cards. Additionally, reducing your deck's size means looping through it more often, which, in turn, means extra horror.
• The Circle Undone campaign:
  • Piper of Azathoth enemy (from "Agents of Azathoth" set) is tough like a tank, hits even harder, relentlessly pursuits investigators and can't even stay dead once slain, despite supposedly providing victory points, as the other cards which comes with its set can revive it. It also has "Elite" trait on top of it, despite not being an actual boss, which protects it from most of the best tools at players' disposal.
  • Witness of Chaos enemy (from "The Clutches of Chaos" scenario) puts breaches (read: Doom) in every location she enters. She spawns in location with fewest breaches, potentially far away from you, and then starts running towards you, due to also being a "Hunter". The only adequate response is meet her head on... where she reveals high Fight and Health values. Fortunately, she awards victory points, which means that once slain, she stays dead.
  • From "Before the Black Throne" scenario:
    • Mindless Dancer enemy is like Piper of Azathoth's little brother: only slightly less Health, even more Fight, and targets your health instead of your sanity. Not only it hits like a truck, it runs like one, too, being able to pass through "empty spaces" and even receiving extra moves when doing so. It isn't Elite, but there are three of them in the deck, and, lacking Victory points, they may return later.
    • "The End is Night!" treachery imposes (increasingly higher) Willpower test, and on a failure, feeds all Doom on Cultists in play directly to Azathoth (or 1 Doom if there's none). If Azathoth ever accumulates at least 10 points of Doom, it's an immediate Nonstandard Game Over, regardless of current Agenda.
• The Dream Eaters campaign:
  • "Myriad Forms" treachery (from the "Where the Gods Dwell" scenario), once drawn, forces to reveal all copies of Nyarlathothep in your hand, and then shuffle them back into encounter deck (but not before they attack you), undoing several turns-worth of progress, potentially costing you the campaign. There are two copies of it in the deck.
  • Web-Spinner enemy (from the "Weaver of the Cosmos" scenario). It's an elusive spider which hides in the distant empty corner and, unless found and smashed in time, puts Doom on its location with every turn (which is permanent, persisting between Agendas), directly contributing to your defeat. As they have "Aloof" keyword, by the time you move to them and engage, you would already spend two out of three actions, and if you fail to kill or exhaust them via evading with the last one remaining, they would still do their black deed.
• In The Innsmouth Conspiracy campaign, a Pursuing Motorcar enemy (from "A Horror in High Gear" scenario), which can attack everyone in a car, doing 2 points of damage; it has above average Fight and Health, meaning that it's likely to attack more than once before the players deals with it. And if it catches someone outside of the car, its damage doubles.
• Edge of the Earth campaign:
  • "Polar Vortex" treachery (from "Deadly Weather" set) sticks to a location, and, if investigators ends a turn there, deals direct damage to not just investigator themselves, but all assets under their control, partners included. While investigator often can survive it, same can't be said about many partners — and those who can, would keep their damage between scenarios. What makes it much more dangerous than its twin sister "Nebulous Miasma" (from "Miasma" set; targets sanity instead) is that it shows up in scenarios where just avoid it may be impossible.
  • "Ice Shaft" treachery (from "Dangers of Antarctica" set) at first looks like yet another "fail the test, get 2 damage" card, but what makes it more lethal is campaign-exclusive frost tokens, which not only can make you fail this test automatically if you draw 2 of them, but this card also deals you extra damage per frost token, resulting in up to 4 damage from just one card (and there are three copies of it). It has a twin sister, "Dark Aurora" (from the "Silence and Mystery" set), which causes all the same troubles, but targets sanity instead of health.
• The Scarlet Keys campaign:
  • "Substance Dissimilation" treachery (from "Outsiders" set) causes you 1 damage and 1 horror for each card in your hand and play area which have a set-aside "hollow" copy. Given all the ways the game can create "hollows" (including other cards from same set), the damage can quickly accumulate to lethal levels (3/3 damage/horror is a boss-grade, and it can go beyond that). If you don't have any "hollows", it instead "hollows" one of your cards.
  • Ancient Raider (from "Dead Heat" scenario), whenever it attacks an investigator, kills a civilian in their location. While attack itself isn't much of a threat (they only do 1 damage), civilian dying is, as it can severely screw investigators later and cause them mental traumas. They have "Retaliate" keyword, so if you fail while attacking them, they kill someone when fighting back, too.
  • Sinister Aspirant enemy (from "Dealings in the Dark" scenario) is like Wizard of the Order, except there're three of them in the deck. Just like the Wizard, Aspirant keeps accumulating Doom if leaved alone, albeit it has different statline. They don't hide in empty locations, and instead use campaign-specific Concealed mechanic, meaning that you have to expose them before killing.
• The Feast of Hemlock Vale campaign:
  • Crystal Parasite (from "Horror in the Rock" set) takes some time to spawn, but when it actually does, it can be very hard to get rid of. It already starts very durable, but during the day, it heals 1/3 of its health after attack, while during the night, is massively increases its stats if you don't kill it in one-two attacks.
  • Poisonblossom (from "The Forest" set) starts relatively weak, but somewhat durable. However, unless killed, it grows tougher each round, accumulating potentially unlimited amount of "overgrowth" each round it stays alive, quickly upping its damage to potentially devastating level, and becoming even tougher (increasing either Health of Fight value, depending on time of the day). While dedicated fighters would have no problems killing it as soon as it shows up, someone weaker may potentially let it grow out of control unless backed up.
  • "Dessication" treachery (from "Blight" set) temporarily makes playing any cards cause damage to investigators, severely weakening investigators who're highly reliant on events (particularly most Seekers, who not only actively use events, but also have low Health and few options to soak damage), as they have to either wait it over, or take the hit each and every time. To add insult into injury, there are several copies of that card, and they can stack.
  • "Psychotropic Spores" treachery (from "Myconids" set) deals you 1 direct horror first time you draw a card each round (something you usually can't avoid doing), which can be very devastating for investigators with naturally low Sanity, as it gives no chance to soak it. It can be discarded, but the chance comes after it hits you the first time, and the test being that of Intellect may force some investigators to rely on teammates' help.
  • "Stolen Light" treachery (from "Twisted Hollow" scenario) gives a choice between increasing Doom, or dropping your lantern in some remote location, forcing you to waste precious time on searching for it, and put yourself at serious risk by going into "Dark" locations.
  • From "The Longest Night" scenario:
    • "Endless Night" treachery either causes massive direct damage and horror to whoever draws it, reduces Doom (which, in this scenario, means delaying your victory and increasing the risk of being overwhelmed by the waves of enemies spawning every turn) or deals damage to the Captives (and keeping them alive is the entire goal of the scenario). No matter which option you choose, drawing this treachery will jeopardise your chances to win, and it is a Peril, so your teammates can't bail you out of it.
    • "Incursion" forces you to pass an Agility test, with difficulty equal to half the Doom currently in play (so it can scale up a lot), and for each point you fail by, it readies one enemy and lets it act immediately, letting them attack you or, worse, the Captives. It has the potential to completely ruin your defence and possibly outright kill you.

---