Bone Devil

If the monster dies outside the Nine Hells, its body disappears in sulfurous smoke, and it gains a new body instantly, reviving with all its Hit Points somewhere in the Nine Hells.

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

The monster makes two attacks and one attack.

. .

. , and the target has the Poisoned condition until the start of the monster's next turn. While Poisoned, the target can't regain Hit Points.