Vrock

If the monster dies outside the Abyss, its body dissolves into ichor, and it gains a new body instantly, reviving with all its Hit Points somewhere in the Abyss.

The monster has Advantage on saving throws against spells and other magical effects.

The monster makes two attacks.

. .

Constitution Saving Throw: DC , each creature in a -foot Emanation originating from the monster.
Failure: The target has the Poisoned condition and repeats the save at the end of each of its turns, ending the effect on itself on a success. While Poisoned, the target takes at the start of each of its turns. Emptying a flask of Holy Water on the target ends the effect early.

Constitution Saving Throw: DC , each creature in a -foot Emanation originating from the monster (demons succeed automatically).
Failure: damage, and the target has the Stunned condition until the end of the monster's next turn.