Is there any evil prankster type monster?

[Yqatuba]

I'd actually be kinda surprised if there wasn't some kind of fey like this. If not I guess you could just make a CE copper dragon.

[Meirril]

More or less look at the Fey list of creatures. All of them more or less fall into this category. Even the 'good' ones.

Mites are the weakest of them, and love cruel pranks. If someone isn't maimed it isn't funny.

Boggarts, Redcaps, Gremlin, Pixie, Saytr, Spriggans the vast majority of well known fey love to torment intruders. Anyone that doesn't play by their rules.

[McDaygo]

Look at the Red Jester

[Artofregicide]

Goblins also fit this niche to a degree, though they're mostly just chaotic and hungry.

[blahpers]

McDaygo wrote:

Look at the Red Jester

*looks it up*

Huh, that seems neat.

*reads mechanics*

O_O

[Claxon]

If you're willing to drop the evil part this is just classic fey.

Heck, fey don't even need to be evil to play deadly tricks because they aren't used to how mortals function. On the first world, dead fey come back to life so playing "tricks" that would result in someones death is just a funny prank to them.