* DemonicSpiders:
** Wizards are able to summon more of themselves, and Necromancers can summon various undead as well. Both can also cast ranged attack spells, teleport away from danger to heal themselves, and the Wizard loves to cast Slow on the player, which can't be cured and has to be waited out, plus the debuff stacks when multiple Wizards cast it!
** [[spoiler: Demons]] will gate in others of their kind, have quickly regenerating health while being tough to hit and dangerous in melee, and can burn or freeze the player from any distance as long as they have a sight line which includes them.
** Speaking of undead, many are able to drain your stats, either temporarily, or permanently (the latter requiring a trip to the temple to recover). Just try running away when your Strength is almost all gone and it takes 30 seconds per step!
* GoddamnedBats: The Smirking Sneak Thief. Steals money and/or items then teleports away. Can take two fireballs to the face without flinching. Though luckily enough, if you are fast enough, you CAN find the thief again later in the level, slaughter it brutally, then get your stolen swag back.
** Not to mention actual bats, and replicating mobs.
** And manticores, especially in the first game when you haven't worked up that much power yet.
** Carrion Creepers, too, in the first game. Things will hit you 20 times for every single action you take.
* GoodBadBugs:
** [[CastFromHitPoints Casting from hit points]] lowers the constitution stat (and thus your maximum HP) until you suddenly die, but if done with the beginning spell Magic Arrow, your HP will stop just shy of zero, allowing you to safely decrease your constitution until it suddenly wraps around and becomes maxed out. Thus, when creating a character, one can set constitution as low as possible in order to raise the other stats, then use this to have all near-optimal stats.
** Casting the Phase Door spell while in a shop will cause all that shop's items to drop in its doorway. Phase door back to that spot, and you can pick them up.