To quote BTVS
"What we once were informs all that we have become." - Darla
Vampires are demonically possessed corpses, Half-Breed Demons. They might act like twisted versions of the human they once were, because of the psychic residue of memories in the human brain. But that soul has departed. Every Vamp you see, that person is burning in Hell, becoming a lower level demonic essence, which will, in turn, possess another Vampire upon Turning. Likewise, everyone who is fully drained to death by a Vamp is Damned to Hell.
Fledglings who don't complete their transformation fall into something akin to Ghouls or Pretas, "hungry ghosts," feeding on the lower level of energetic cast-offs, like dung or the newly dead.
The oldest Vamps are possessed by True Demons who spawned their insidious Bloodlines. Older Vampires must feed fully to look human. The more ancient, the more demonic they are.
