Undead

An Undead is a living creature that has been brought back to life. A proper Undead possesses the soul of the original owner, ripped back to the physical realm, with soulless undead being technically bone or flesh golems.

It is the distinction of being placed back into the wreck of their own body that prevents Demons and Kodama from being classified as undead.

Skeleton
A Skeleton is what one would expect, an Undead creature composed of a creature's skeleton, typically after its tissues have long since rotted away

Remnant
Legends say when a mortal is struck down by one of the gods, their body and soul is completely obliterated, and yet, some fragment of their existence remains. Over time, this fragment feeds off of malevolent energies and other fragments until it gains some semblance of form.

Remnants are extremely powerful undead, infused with the divine power that was used to slay them. Similar to ghosts, the Remnant’s body is insubstantial, though there is no passing on to the next world for them. Instead the Remnants live only to haunt the oldest ruins of Castores, and to feed on the hopes and dreams of any mortal foolish enough to come upon them.