The iZombie mythology classifies supernatural creatures using the Egyptian concept of an oversoul (memories, rational thought) and an undersoul (passion, animalistic). Central character John Amon lays it out thusly:
- Ghosts: A roaming oversoul.
- Poltergeists: A roaming undersoul.
- Zombies: A revived body with only an undersoul, hungering for memories and thoughts.
- Vampires: A revived body with only an oversoul, with an animal hunger for blood.
- Revenants: A revived body with both undersoul and oversoul intact (but requiring human flesh to sustain itself).
- Werewolves: A person sharing their body with an animal undersoul.
- Possessed: A person sharing their body with (or controlled by) a human oversoul.