.It is explicitly part of the Cthulhu Mythos of H. P. Lovecraft. Like most of his works, it is set in the early 20th century. You are given control of the main character right as they arrive at the entrance of the so-called Church of Starry Wisdom, an inconspicuous chapel in the middle of the forest that is nevertheless a home to a notorious cult. Their underground lair is large, and at the very bottom of it lies the object of their worship, The Shining Trapezohedron, which is said to reveal all secrets of the universe. The cultists will do anything to protect it; if you are a dedicated player, your character (or rather, numerous characters) will likewise do anything to get to it.
Compare to Door In The Woods, a commercial Roguelike set in a world that has already suffered a Lovecraft-inspired apocalypse.
The Tropes of Infra Arcana:
- Asteroids Monster: Worm Masses are one of the most fragile opponents in the game, to the point even the Rogues are normally capable of instantly destroying them with their dagger. However, they have a high chance of splitting upon death, and the player can potentially get surrounded if they didn't take care to fight them in some corridor one-by-one.
- Back Stab: An attack performed upon an unaware enemy (as indicated by their blue background) will do 50% additional damage, and is almost certain to connect. Daggers get an inherent bonus to such attacks as well. Rogues can also eventually get a Vicious trait that raises said damage by 150%, and Ruthless then adds on another 150%.
- Blackout Basement: Once you go from the abandoned church building above ground, and descend into the actual catacombs, the darkness can at times be overwhelming, making it impossible for a human to see anything outside of a single tile radius around you. You do start with an Electric Lantern, but it'll only last for 100 turns, unless you have invested into an Electrically Minded trait that'll double its duration (amongst the other bonuses).
- Bloodless Carnage: Averted. Not only are the enemies' remains on the ground portrayed as red, but even the walls next to them will switch to red to signify being spattered with blood. Moreover, that gore will actually disturb many of the monsters you encounter as well!
- Bloodsucking Bats: Vampire Bats. Like the Giant Bats, they are said to be as tall as a human, but they can also directly heal themselves with every successful attack they inflict on you.
- Call A Hitpoint A Smeerp: Spells are cast using Spirit, rather than Mana. Oh, and running out of Spirit is an instant death. For added fun, casting any spell never has a fixed Spirit cost, but rather picks one value out of a range, so it is possible for a spell you tried to cast to straight-up kill you instead. (Though you are at least given a warning when this is a possibility, and may choose to abort spellcasting and wait for the Spirit to regenerate to a safer range instead.) Did we mention that some monsters are able to diminish your Spirit values with their attacks?
- Color-Coded for Your Convenience: Played straight with the Huge Spiders: they will inflict Paralysis if they are White, Blindness if they are Green, and Weakness if they are Red.
- Creepy Ravens: These can appear on the very first floor, and will usually make their presence known before you even see them, simply through the eerie flapping of their wings. While they are unlikely to kill you on their own, their pecks have a high chance of blinding you for a couple of turns (unless you possess eye protection such as a Gas Mask), which makes them very dangerous if they are accompanied by any stronger enemies. They can be shot at effectively if they haven't yet spotted you, but once they did, your ranged accuracy will go down to 10% or so.
- The Cult: The Church of Starry Wisdom; what else? While their members are simply fellow humans, they all have ways to make you fear them:
- The basic Cultists are likely to try casting spells, but only know one and will nearly always fail at it. However, they will always wield firearms: mostly M1911 Colts like yours, but some will instead carry Pump Shotguns, Sawn-Off Shotguns, or even Tommy Guns. If you happen to get the drop on a Cultist, then shooting them while unaware is practically bound to kill them in that turn and net you their weapon and/ ammo. If you are not so lucky, then even the pistol users will normally inflict a wound with their shot; Cultists with shotguns, let alone Tommy Guns, are straight-up capable of an One-Hit Kill.
- Zealots are their second-most frequent variety. These have torn their eyes and tongue out in their devotion, and now lash themselves with a Spiked Mace, which both does hefty damage and has a 25% chance of stunning the victim and thus exposing them to more sustained punishment. The worst thing is that they frighteningly tough, being easily able to tank several shots from your Colt M1911, and even a Molotov is unlikely to stop them on its own. While they are theoretically supposed to mainly appear below floor 3, discovering them even on the first floor is not of the question; if you failed to avoid triggering them (since they can only track the player by sound), lack a Shotgun/Tommy Gun, or even some Zombie Dust/malign potion to make shooting them down easier, then you are in for a bad time.
- Cultist Priests only bother to carry enchanted ritual daggers with them, but they know an array of spells, from their equivalent to an Invoker's Darkbolt, to a range of debuffs, to self-healing and the ability to summon Rats.
- Wizards are encountered in the late game simply wiser, tougher Priests with a larger spell repertoir and which are way more difficult to get rid of on the first turn. Setting them on fire to at least impede their spellcasting is often a good idea… as long as they don't paralyze you while your Molotov is lit, but not thrown!
- Enemy Summoner: Major Clapham-Lee was originally an undead character in Herbert West–Reanimator. Here, like in that story, he "commands the undead legions", and so he will summon several Reanimated Corpses (and potentially Bloated Corpses) out of seemingly nowhere, along with another undead pal from that story, Dean Halsey. This always happens on his second turn after sighting you, unless you have managed to either destroy him in one turn, or paralyze him, and then finish him off before he gets the chance to recover. If neither is an option, you are better off lightning a Molotov as soon as you spot him and hoping you won't get caught in the flames, or that you possess a potion of Fire Resistance if you do.
- Eye Scream: The ravens' pecks have a high chance of blinding the player for a couple of turns. Eye protection counters this, though, and War Veterans in particular are advised to put on their Gas Mask as soon as they start hearing the flapping of wings in the area.
- Face–Heel Turn: Though they vowed to destroy the Trapezohedron, the Exorcist will still end up making a pact for knowledge, binding themselves to serve Nyarlathotep.
- Fighter, Mage, Thief: The four available human character roles are a War Veteran, Occultist, Rogue, and Exorcist, with the former three matching up well with these archetypes, while the Exorcist plays like a subtype of Mage. Of course, there is also the role of a Ghoul, which is like a Barbarian taken up to eleven.
- Giant Spider: The Huge Green, Red, or White Spiders, which are encountered on the later levels. They are both tough, and move faster than the player character, and their damage is scary even if the player possesses the Iron Suit. Worst of all is their ability to blind, weaken, or paralyze the player once they started attacking, making dealing with them at range (or straight-up avoiding them) paramount.
- Healing Spring: Gleaming pools can be found in the deeper floors. Bathing in them instantly heals all your Wounds.
- Hulk Speak: If your character gets Frenzied, all of the text describing the actions they may take morphs into Hulk Speak.
- I Am a Humanitarian: Ghouls cannot regenerate health, and heal through feasting upon corpses instead, which easily includes human corpses. Getting a Ravenous trait allows them to occasionally feed on the living enemies while attacking them in melee as well.
- Innate Night Vision: This is possessed by the Ghouls.
- Life Drain: This is what the Vampire Bats' bite does to their victims (i.e. yourself).
- Lightning Gun: The Mi-Go wield these, which complement their spellcasting powers. You can pick one up after defeating them too, but their average damage (8.5, same as a Colt) and the fact they are Cast From Hitpoints make them into a ranged weapon of last resort.
- Machete Mayhem: Machete is the default weapon of the War Veteran. It is the only one of the three starting weapons that is not silent to wield, but it is also the most powerful, dealing damage in the 3-11 range.
- Magic Missile: The Darkbolt spell, and one of the two Invocation-focused Occultists start with. It deals 4-9 damage, is guaranteed to hit its victim, and has a chance of paralyzing the target (which then boosts accuracy for your conventional melee/ranged attacks into 90-98% range). However, the projectile has a mind of its own, and so if there is more than one target, it'll determine for itself which one it's going to strike. If there are no visible targets at all (i.e. if the player has been blinded), then it'll fizzle out immediately.
- Mana Potion: Called a Potion of Spirit here. Occultist characters automatically start with one of these.
- Molotov Cocktail: All of the human characters start with a couple of these, and they are exactly as dangerous as one would expect, even making the unique "miniboss" characters comparatively trivial. However, keep in mind that it takes two turns to deploy a Molotov (one to light it, and one to throw it), and so enemies may well sufficiently close the distance to make it impossible for the player not to get caught in the splash damage. Even worse are the spellcasters, who may paralyze you right as you are holding a lit Molotov in your hand. Since being set on fire yourself doesn't just deal consistent damage, but also prevents you from shooting firearms, spellcasting, or reading scrolls, and that fire can also spread from where it was originally ignited, as well as spreading smoke, both are very bad news. If you happen to have identified a Potion of Fire Resistance, it's often worth consuming it well before trying to throw a Molotov.
- Nominal Hero: The majority of the classes simply want to rob the cult's treasures and knowledge, but they don't engage in the same evils that the cult does. Until the ending has them make a pact for knowledge, in exchange for spreading death and madness across the world.
- Non-Combat EXP: All of the XP is exclusively obtained through discovering new things. Descending to a new dungeon level immediately adds 5%: detecting a trap or a secret door adds 2, finding a monster you have never seen before is worth between 3% for basic monsters like Rat-Things to 10%+ for unique minibosses like Keziah Mason, finding unknown potions or manuscripts immediately adds 8%, identifying the purpose of the unknown Rods or Strange Devices can add 15%, and reading runes on the Obelisks immediately grants 20%. There are also two ways that are more chancey — some Fountains may give "more insightful" bonus and +1% XP if you drink from them, but it's also possible to get outright negative effects from a Fountain, while gongs may give a huge experience boost when rung, but are more likely to just deafen you for a considerable amount of time.
- Not Using the "Z" Word: The undead are called Reanimated Corpses here. Justified, since the game is set around 1920s, when the word "zombie" had yet to enter popular lexicon. They will occasionally drop the paralyzing powder that actually is called Zombie Dust, though, which presumably refers to the Haitian concoctions used to create the original "zombies" — plantation workers who were drugged out of their minds to ensure complete obedience.
- Optional Stealth: The game has a reasonably detailed stealth system, which includes several levels of awareness for the NPCs and takes both the light levels and noise made by the actions such as melee attacks, gunshots, swimming or wading through the water, or opening/kicking down doors into account. Given the overall difficulty level, you'll likely resort to stealth at least some of the time. Rogue characters also start with a +45% bonus to remaining undetected.
- Our Ghouls Are Creepier: A Ghoul is one of the five starting background options. They get the largest starting HP pool, but cannot regenerate it, and must feed upon corpses instead. They also lack any starting inventory whatsoever, but are immune to sprains and disease, and are obviously less fazed by seeing other monsters than the humans. Their eyes can also see in the dark, but are apparently worse at focusing because of it, resulting in a reduced accuracy with any firearms, or even when throwing things.
- There are ghouls roaming the later levels as well. They will be allied to a Ghoul player character, but the others will have no such luck if they run into a pack of them.
- Ghouls can also learn a "Foul" trait. This makes it so that worms may burst out of the corpses of your enemies and attack any remaining opponents! It can then be upgraded to Toxic, which confers both a poison immunity and a chance to poison the enemies with your claws!
- Our Goblins Are Different: Bog Tchers are an original creation of Infra Arcana, and while described as "dwarfish" in appearance, their combination of small size, cruelty, and inventiveness clearly evokes goblins. Since they are shorter and weaker than humans physically, they are pretty easy to beat down in melee. At range, however, they wield their Spike Guns, and if you don't kill them before they get to use them, a shot from one will almost certainly pin you to a wall, both immobilizing you, and making you take further damage during the attempts to tear free.
- Our Zombies Are Different: The Reanimated Corpses can be potentially encountered on the first level, and are one of the toughest early enemies. They move at pretty much the same speed as the player, so outrunning them once they spotted you is difficult, possess as much HP as the player, if not more, and their damage quickly adds up: fighting just two of them at once in melee is usually a very bad idea.
- Moreover, these corpses have a hefty chance of Infecting you with their rotten claws. Infected status doesn't mean much on its own, but will quickly turn to Diseased unless promptly treated with your Medical Bag. If you had just brought one down, but got Infected, it's tempting to start healing immediately, and forget to deal with the leftover corpse (usually by standing right above one and kicking downwards), which will then just stand back up again at full health.
- For extra fun, a Reanimated Corpse going down may occasionally lead to its intestines bursting out of its stomach and crawling out to attack you on their own. While they are essentially equivalent to a Worm Mass in stats, and thus easy to deal with, the mere fact of this happening adds around 10% of Shock all on its own, and may end up pushing the character into 100% if this happened unexpectedly as they were about to move on to the next level. The same thing can also happen with their hands, though it is somewhat less dramatic.
- Poison Mushroom: The unidentified potions you find can easily have harmful effects. The Potion of Poison and the Potion of Paralysis are the clearest examples. However, carrying them for long enough will at least identify them as "Malign" (same as with the Benign potions), and you can then try putting them to good use by throwing them at the enemies.
- Rat Stomp: One of the earliest enemies you will likely encounter are Rat-Things. While they are actually man-rat hybrids with disturbingly human faces according to the description, they still go down easily. War Veteran characters will likely not even take any damage from their bites due to the Flak Jackets they wear.
- Actual rats can be encountered too, though they are only found on special occasions. This includes being summoned by the Cultist Priests or Keziah Mason (the "mother" of Rat-Things), or showing up as a dozen-strong pack as a potential ambush when the walls of a secret room near the player suddenly collapse (as an alternative to a Rat-Thing or a Reanimated Corpse/Bloated Corpse ambush). In all cases, they are predictably weak, but can be annoying due to inflicting the Infected status.
- Regenerating Health: Hitpoints will regenerate automatically over time, unless you are playing as a Ghoul. Receiving a high amount of damage at once, however, will leave a Wound, and these result in a permanent debuff unless treated with a Medical Bag over a considerable amount of turns. Death occurs once your character has either run out of hitpoints, or accumulated five wounds. A Survivalist trait also makes wounds somewhat more bearable, and grants immunity to the Diseased status (which may otherwise occur if Infections from certain nasty enemies are not treated promptly with a medical bag), while Rapid Recoverer boosts the regeneration rate. The various Oozes are particularly annoying to deal with due to their high regeneration capabilities.
- Religion is Magic: Despite refusing to learn magic from manuscripts, the Exorcist can still cast magic, learning it as a trait.
- Religious Bruiser: The Exorcist, who enters the church in order to cleanse it of all the corruption within. Interestingly, their holy symbol appears to be an ankh, suggesting them to be a Coptic Christian or an offshoot of that faith.
- Sanity Slippage: Like any Lovecraftian game worth its salt, Infra Arcana has a sanity meter, which consists of two tier. As such, things like sighting the disturbing monsters, carrying unholy artifacts, using occult powers, staying in the darkness for too long, or spending too much time in that accursed lair in general accumulates Shock, while standing in the light temporarily reduces it, and descending to the next dungeon level clears Shock completely. If Shock reaches 100%, your character snaps in some way (ranging from laughing uncontrollably, to fainting, or even gaining a permanent phobia) and then, the Shock value is reset down to 0%, but the Insanity value rises, and this cycle can potentially go on until your character truly goes irrevocably mad at 100% Insanity.
- A Potion of Fortitude is highly valuable both due to making the player immune to all the psychology-related status effects, and for completely clearing any accumulated shock. Quaffing from the fountains and getting the "refreshing" message doesn't just slightly restore Health and Spirit, but also lowers Shock by 5%.
- Savage Wolves: The wolves can be encountered from the first floor of the lair onwards, and they typically come in packs. They'll move faster than a human as well. Still, War Veterans can consistently out-melee them one-by-one, and Invoker Occultists will get good results through casting Aura of Decay and keeping their distance until the entire pack collapses.
- Short-Range Shotgun: Both shotgun types appear inferior to Colts when fired at a distance.
- Shotguns Are Just Better: There are two main varieties: the normal Pump-Action Shotguns deal 6-18 range instead of Colt's 5-12 and have the capacity of 8 shells; however, their damage appears inferior to Colts at range, and they are also reloaded shell-by-shell. Sawn-Off Shotguns are obviously even less effective at range and only fit 2 shells, but their damage of 8-24 up close is nothing to sneeze at. In all, sawn-off shotguns are better at putting down the singular tough enemies that need to die ASAP,
- Tommy guns are still more powerful than either shotgun, dealing damage in the much more consistent 20-30 range. However, they consume 5 bullets per burst, so even if you find one with a full drum, you'll still get only 10 bursts out of it.
- Shout-Out: The cultists' chanting and raving are taken directly out of Blood.
- Smoke Out: There are Smoke Grenades, and War Veterans in particular begin the game with a few of these. They will obscure the opponent's field of vision, but the same will happen to you once the smoke spreads towards your location, and the acrid smoke will also hurt your eyes, lungs and throat. Smoke is also generated whenever something is burning (usually from the Molotov Cocktails you have thrown), and explosions will kick up clouds of dust, though these will dissipate in a turn or two.
- War Veterans start the game with a Gas Mask, which will protect them from all the harmful gases, including the dungeon's gas traps, which inflict confusion status for several dozen turns. However, the Gas Mask's filter only has a limited lifespan, and wearing the mask both reduces their accuracy and makes it harder to detect hidden objects (traps included), or even the enemies trying to sneak up on them.
- Spike Shooter: The Bog Tcher Spike Gun. It is weaker than the firearms in terms of raw damage, dealing half the average damage of even the Colt pistols. However, their true power lies in their ability to knock back the victims and pin them to the wall, thus immobilizing them, raising the accuracy of all the subsequent shots and making the victim take further damage on every turn they attempt to wriggle free.
- Squishy Wizard: The Occultist characters are the closest thing to a wizard in the setting, possessing the most Spirit points and regenerating them the fastest. They also get to drain occult traps to restore some Spirit Points, will occasionally block enemies' spells, suffer a halved Shock penalty for casting anything, and get to specialize in a domain between Clairvoyance, Enchantment, Invocation, and Transmutation. To compensate for these advantages, their max hitpoints are reduced by 2 in comparison with the others.
- Super Spit: The Spitting Cobras live up to their name with a ranged venom attack. Bloated Corpses spit acidic pus.
- Tactical Door Use: Every door in the lair that can be opened can also be closed (assuming the door wasn't jammed when you first found it, forcing you to kick it down). Closed doors will successfully stop the various animals, but not cultists; however, Rogues begin the game with several metal spikes in their inventory, which will permanently bar the doors.
- Reanimated Corpses do not know how to open doors, but they will try to beat them down, which can take anywhere from one turn to dozens depending on your luck. If it's not a normal wooden door but a barred one, then you can shoot at the zombies or other assailants through the gaps in the metal bars. The flip side is that the intelligent enemies will likewise be able to shoot you or cast offensive spells at you through the very same gaps.
- Ten-Second Flashlight: Your Electric Lantern will expire in 100 turns by default, which can happen very quickly. Players often take their chances even in pitch-black areas, and deploy them exclusively when rushing to the end-level stairway, hoping to stave off Insanity through their -20 Shock effect.
- Token Good Teammate: While most of the classes simply want to claim the Trapezohedron for themselves, the Exorcist desires to destroy it, so that it doesn't tempt anybody else, along with putting an end to the cult instead of simply claiming its knowledge and treasures.
- Unidentified Items: Played straight with all of the potions and manuscripts you find. However, carrying both of them for a while will eventually give you a feeling as to whether that item type is benign or harmful. The Occultists who specialize in Clairvoyance also get an Identify spell; otherwise, happening to consume a Benign Potion that was a Potion of Insight will allow you to identify an item (along with granting some experience on its own.)
- Zombie Puke Attack: Bloated Corpses spit acidic pus, and they can do so over a pretty good distance as well, so watch out!
