YMMV / Pixel Dungeon

• Demonic Spider: Several.
  • Most "mutant" enemies, a rare, tougher version of the normal one, with an added status effect.
  • There is a slight chance that you will encounter an enemy from the next group of floors on the last floor (before the boss) in that group. Of course, on the extremely rare chance this is combined with the example above, kiss that run goodbye.
  • Sewer Crabs, thanks to Early Game Hell, and them being faster and far tougher than anything else in that set of floors. They appear in the second half of the first leg of your journey. Good luck.
  • Crazy Thieves. They take an item from your inventory. It seems to always be your best wand, a key, or (if you use a Wand of Firebolt), a valuable Scroll to get burnt up. Their mutant variant also inflicts blindness.
  • Dwarf Monks. They hit hard and fast, and have a very high tendency to disarm you, which is made worse by them being the only enemy to do this (See Scrappy Mechanic below). Also, their mutant form also paralyzes you.
  • Evil Eyes. They have a VERY powerful armor-piercing laser attack (which unlike every other enemy, they always use instead of switching to inferior melee tactics), and deadly accuracy. Because of them (almost COMPLETELY because of them), most players advise just making like a bat outta hell through the final area.
    • Actually, almost any enemy with magic attacks become this for the same reason. Gnoll Shamans also deal extra damage to you when you're standing on water (because they attack with lightning bolts). Dwarf Warlocks also weaken you, halving strength and further lowering your melee damage.
• Game-Breaker:
  • The Dew Vial. This item will prevent lethal damage, heal you to full, has no negative side-effects and is refillable to boot, unlike its brother the Ankh. And, all it requires is finding ten of a common item while at full health that randomly drops from the equally common vegetation... that you can even grow yourself.
  • Wand of Firebolt. Unlike other algebraically growing wands, its damage scales quadratically. Also, it sets enemies alight, as well as barricades (and bookshelves), negating the need of a Potion of Liquid Flame or Seed of Firebloom. It can even cook Mystery Meat! It only has the trade-off of fire itself, it lights vegetation and doors aflame, which will all too often include you. However, even this can be used tactically, as crowd-control of high-dodge One-Hit-Point Wonder wraiths becomes trivial if led to a grassy area.
  • Wand Of Flock. Not only a Lethal Joke Item, but useful for crowd-control. It creates a massive number of impassable, invincible, entirely passive sheep that stay for turns on end. You can also take advantage of the Multi-target damage bonus offered by the Wand Of Disintegration.
  • Ring of Haste. It slows time passage for the wearer. This therefore lets you move and attack at several times the speed of enemies, and saves you from the aggressive hunger clock. The only problem is waiting out harmful area effects, or it would be if there wasn't a wait button with a one-turn constant.
  • Ring of Evasion. Ups your evasiveness, making you hard to hit on egregious levels.
• Goddamned Bats: Vampire Bats. They do drop healing potions, however.
• Scrappy Mechanic: Dwarf Monks knocking off your weapons. Should it happen, you'll need to waste a turn picking up your weapon and another equiping it, during which the Dwarf Monk (and possibly other enemies) will still be attacking you. And they can knock off your weapon the turn you equip it. If the RNG is feeling particularly merciless, you can get stuck in a nasty Cycle of Hurting where you try to equip your weapon, the Monk knocks it off, you try to equip it again, the Dwarf Monk knocks it off again, ad infinitum until you either kill it or it kills you.