History DemonicSpiders / EtrianOdyssey

* Mandrakes are a first stratum enemy in the first game, but in ''Heroes of Lagaard'' they don't appear until the fifth, towards the end of the main game. There's a ''very'' good reason for this. The Mandrake's only skill, Scream, attempts to inflict instant death on the ''entire party'' at a not-insignificant chance of 35%. Their best stats are conveniently Luck, making them more likely to inflict it, and Agility, letting them use it faster while also being more likely to dodge any attempts to frantically take it out. It at least only starts using it after taking damage, but that doesn't apply to blindsides, where it has a decent chance of openening with it and wiping the party before they can even act (and they can come in groups). ''The Fafnir Knight'' essentially converts them into weaker Evilroots from ''The Millenium Girl'', with the instant death chance of the skill (now Last Cry) being much higher but being interruptable with Blast Grenades, and it says a lot that this version is still considerably fairer than the original.

* ''The Drowned City'' has the Longicorn Beta on the final floor that can summon multiple enemies at any time, and then throws them for high damage to the entire party. It's also highly durable, which makes it difficult to shut it down with [[StatusEffects statuses]] long enough or kill fast enough to stop it from throwing enemies.

! ''Etrian Odyssey'' and ''The Millennium Girl''

! ''Heroes of Lagaard'' and ''The Fafnir Knight''

! ''The Drowned City''

* Forest Shrimp, found in the Waterfall Woods behind the Star and Moon Doors. They have a special attack that hits the entire party and has a high chance of causing paralysis. They're also tough as nails, being highly resistant to both physical damage and Ice damage (which is a problem if you're hunting Golden Idols). Even more irritatingly, they tend to show up with Demon Octopodes, which have an attack that binds your entire party's legs, making it that much harder to escape them.

! ''Legends of the Titan''

! ''Beyond the Myth''

!''Etrian Odyssey Nexus''

* The Dinogator makes its return as the strongest FOE in the game, and this time it holds nothing back -- the Pout skill normally reserved for when it TurnsRed is now used ''on the very first turn'', hitting for [[ThereIsNoKillLikeOverkill over 2000 damage per hit]]. There are two ways to go about this fight: either force it to sleep to avoid the turn 1 Pout, or capitalize on Pout to kill it with Curse backlash damage. Fortunately, it's very difficult to encounter the Dinogator by accident, so it borders on BonusBoss.

* Coffin Demons in the third stratum and Hex Steeds in the fifth behave similarly: they have a multi-hitting attack that can leave behind a mixture of ailments. Coffin Demons inflict poison, curse, or blind; Hex Steeds inflict paralysis, curse, and petrification. They also are tankier than every other random encounter in the stratum. Disable them quickly or your party will meet an untimely end.

* The Dinogator makes its return as the strongest FOE in the game, and this time it holds nothing back -- the Pout skill normally reserved for when it TurnsRed is now used ''on the very first turn'', hitting for [[ThereIsNoKillLikeOverkill over 2000 damage per hit]]. There are two ways to go about this fight: either force it to sleep to avoid the turn 1 Pout, or capitalize on Pout to kill it with Curse backlash damage. The Dinogator here is practically a BonusBoss, and it's very difficult to encounter it by accident.

* ''The Drowned City'' has the Longicorn Beta on the final floor that can summon multiple enemies at any time, and then throws them for high damage to the entire party. It's also highly durable, which makes it difficult to shut it down with [[StandardStatusEffects statuses]] long enough or kill fast enough to stop it from throwing enemies.

* Petaloids their variants in ''Etrian Odyssey'' loved nothing more than to chain-sleep your entire party, thus allowing the other enemies to unleash a world of hurt on you. They appear in ''Legends of the Titan'' as well, although thankfully they'll only target one party member... unless you damage them.

** Venomflies deserve special mention here. In the first game, they showed up in the first stratum, with an attack that poisons one member of your party. Annoying, but manageable. In the second game, they showed up, still in the first stratum, with at attack that poisons your ''entire party''. Then, in the third game, they showed up in a locked area of the first stratum, with an attack that poisons one member of your party - at a rate of ''350 HP'' per turn of poison damage.

* Any enemy who has Instant Death abilities, especially ones that hit multiple characters ''and come in packs''. While some are balanced out by requiring a turn to use to give time to bind or use a sonic bomb to stop it, it's still easy to ether mess up or have them paired with disabling enemies and quickly end a game.

* Several monsters can perform {{Combination Attack}}s, with one or more monsters "standing ready" and another monster performing the attack itself with the aid of its partners. If at least one of the participiant monsters isn't killed before the attack takes place, or if you at least don't render the main user unable to use the skill (binds, Panic, etc.), expect to see at least two or three dead bodies in your party at the end of the turn or even a GameOver.

* A clear example from the second game are Gigaboars, since it's the stopping point for many in the second stratum, forcing a serious training and reequipping stop. Gigaboars don't have much HP, all in all -— 180 is a pretty manageable amount for a party in that level. But they hit like mack trucks. As in, if you're using a Ronin or Dark Hunter in the front lines? Oneshotted. And they have pretty decent speed too, so you can't use the most damaging attacks, since they're slow and you'll give them the first action that way.

* Shielded Phasmids in the secret areas of the Tutelary Forest have two types of {{Counter Attack}}s. The first causes it to retaliate for every of its allies that have been felled this battle, which can be easily accomplished if you're not careful with area-of-effect skills. The second causes it to counter physical damage. Only three classes out of ten can inflict pure elemental damage without any physical component. Both attacks hurt really hard and can cause unsuspecting parties to wipe out.