Ghosts

Summary
Ghosts are the spirits of humans that die without a soul to be judged. This is usually a result of their soul being destroyed or eaten by Demons or Angels. Ghosts live in Purgatory, basically just earth however they're unable to speak or touch any living human. Ghosts can see all Celestial Beings and can be carried to Heaven or Hell.

Ghosts are spirits of pure energy. They do feel emotions but do not possess a soul. Similar to how demons eat souls, ghosts are able to consume each other (but not souls) to gain power. However, if a ghost eats a massive amount of other ghosts their body will contort into a monstrous creature.

Reapers
Reapers are titles given to Ghosts who create contracts with Angels to reap human souls. Angels in charge of taking souls sometimes outsource their work to the wandering ghosts in Purgatory. They provide the Reaper with a weapon of their choice, engraved with specific ruins that allow it to be used on humans, and a massive list of names and times (usually billions of people long, some of the people weren't even born yet). The angels agree to bring the reaper to heaven after they reap the souls of every person on the list.

Some Reapers eventually give up on completing the list and start killing each other to gain power or to collect weapons