- DnD 5E does not mention that undead are damaged by healing spells. Vampires plus spawn are resistent to necrotic damage and radient damage suppresses their self healing.
- personal opinion: Creatures that behave like sentient beings have a soul in the DnD universe.
I like the Pillars of Eternity lore. Undead are created when the soul does not leave the body after death or when somebody puts a soul into a dead body. There is a lich arch age in both games.

Prof. Dr. Dr. Mad S. Tist

World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already