Raven Crowking said:
The whole idea of "Gotcha" monsters is actually sorta weird, IMHO. What qualifies a monster as a "Gotcha" monster and not just a monster? Why don't we say "The ogre hit you with a club -- Gotcha!"?
A Gotcha! monster is a monster that exists solely because adventurers exist and do certain things for the sole purpose either damaging adventurers or screwing said adventurers out of hard-won resources and equipment (or as a faux-balance tool for a campaign that has 'gotten out of hand'. Given out too many magic items? Trot out the Disenchanter!). It's a heavy-handed and usually nonsensical creature. In the same vein as this are creatures that exist solely to stop, block or nullify a specific character class ability.
All they usually serve to do is make would-be bold adventurers into whining, cringing accountants who want to map corridors with protractors and laser sights.
The old cursed magic items are another form of Gotcha monster. Nothing says 'fun adventuring' like finally winning through a tough adventure to find that the cool item you thought you were getting is acutally not only worthless but now you have to go on a special side adventure just so you can get rid of it.
Once in a great while, these can be used to good effect. Like, maybe once or twice a campaign lasting several years. Similarly, an adventure dealing with a cursed item can be a well-done thing frought with honest peril.
The way it almost always works, though, they are a smothering inconvenience, and a way for the DM to laugh at the 'stupid' players. "Man, you didn't think to stop and
sniff the monster before you attacked it! It's not a hobgoblin but a rare Hemogoblin. It blows up for 50 points of damage. You're dead."
What I hated most was the faux-evolution rationale for such creatures. As if that made them OK.
* Adventurers wear a lot of heavy metal armor. Introduce the Rust Monster.
* Thieves listen at doors. How dare they! Introduce the Ear Seeker.
* Mages covet magical books and store their most important class ability on paper. Introduce the Bookworm that only eats magical books.
* Beholders are terrifying creatures of vast power and evil intent. Any encounter with one, especially at lower levels, is sure to be a super-tough fight and result in at least a couple of dead party members. OMG! There's one now! Quick, drink your potion of Heroism. Cast Haste or Stoneskin. Use charges from that wand! Expend a couple of your once-a-day ability uses! Charge! Boom, haha! It's a Gas Spore. Now you're all going to sprout mushrooms out your ears.
* The Nilbog. 'Nuff said. (Indeed, something like half the monsters from the original FF).
I'm sure people can think of others.