I do not mean in the sense of a prestage class or something nor that is an undead of another sapient population.
a life form that is undead from birth to death that is effectively an undead species?
as that seems sufficiently out there and fantasy for it to be worth a shot?
I'm not sure how a life form could be undead from birth to death - isn't that contradictory?
Explorer's Guide to Wildemount
added Hollow Ones as an official D&D race. They are people who have been killed and subsequently become "beings whose souls have left for the afterlife, yet whose bodies still retain a fragment of their former selves." Marisha Rey's current character on Critical Role
, Laudna, is a Hollow One. I like the concept a lot, especially the Unsettling Presence ability: "As an action, you can unsettle a creature you can see within 15 feet of you. The target has disadvantage on the next saving throw it makes within the next minute. Constructs, undead, and creatures that can’t be frightened
are immune to this feature. Once you use this feature, you can’t use it again until you finish a long rest."
I don't know how you would have undead that is not derived from a formerly living being. Isn't the whole concept of undeath something that lived, died, and then came back but without all of its previous biological functions intact? If something was born, grew up, etc. how would it differ from a living being?