Hellish Weapons

The creature’s weapon attacks are magical and deal an extra X poison damage on a hit (included in the attack). (Erinyes, pp. 73, MM) Hellish Rejuvenation
If the creature dies in the Nine Hells it comes back to life with all its hit points in 1d10 days unless it is killed by a good-aligned creature with a bless spell cast on that creature or its remains are sprinkled with holy water. (Lemure, pp. 76, MM)