Abmortals are humans that - in what way they managed to do this, varies- have circumvented death. Each abmortal is unique, but many have to substain themselves by harming others- be they humans or ghosts. Having left humanity and its attendant fragility behind, abmortals can be truly loathsome, immoral creatures; often, they manifest few outside changes to appearance that might indicate their undying natures.
Created as they are by confluences of unique events, many abmortals have a decided ignorance of the supernatural world in general. It is only the fact of their depredations on the karmic balance of death (as some might poetically put it) that brings them into regular conflict with other supernaturals (namely Bound).