Vaath

Ah yes: the Vaath. Monte Cook gettin' his edge on, back in 1990s Planescape. The Planes of Conflict boc mooted them in its Monstrous Supplement.

This locates the monster in Cathrys, Carceri. It's some sort of demonic reptile with an insectoid shell, long fangs and a hollow ten-foot(!) tentacle-tongue. Its fangs are venomous and, failing saving-throw, kills you in 1d4+1 rounds. The kicker is that the vaath doesn't want to kill you.

Enter that tongue, baby! This will, if not stopped, find the spinal-column; the vaath will then gaily rip its paralysed victim into pieces, some pieces saved for trophies. The vaath loves an audience; others watching this gruesome display stand to be stunned 1-3 rounds in horror.

They are not fiends although can be "summoned" from these infernal reaches. They have male/female sexes so, we suppose, can breed. Left alone they "live in packs" but fiends are known to keep some around "as guards, torturers, or even pets".

So yeah: SOOPER EDGY. Half the two-page summary is a short-story describing an encounter. Third-Edition players got 'em in the Book of Vile Darkness where-else. This version is even worse, as it has the ability to broadcast its sense of taste to nearby creatures so anything it tastes will be tasted by anything around it, so both its victim and their nearby friends will learn what the victim's insides taste like as they die.