The Celestial Cycle
A big important part of the way the entire world works is the life cycle of a celestial. There's more to it than just what's shared here but this is a very good starting point for how the world works, and the different levels of beings.
A Celestial is an immortal; demon, angel, or otherwise.
An Angel (i.e, Aelthiel) is the purest form of a celestial, born of Heaven and still residing in/ working with Heaven.
A Risen angel (i.e, Dandelion) is an angel that was previously a fallen angel that has regained its wings or a demon that has undergone the rite of ascension.
A Fallen Angel (i.e, Jake) is an angel who's connection to heaven has been severed. There are many reasons why this could happen.
A Mortal (i.e, Benjie) can be a way a celestial may refer to a human, or anyone who does not possess an immortal body.
An Imp is a fledgling or baby demon (or a suppressed demon in some cases, but for the purposes of this graph it's referring to a baby demon) They can be born or made in many different ways and are huge nuisances.
A Lesser demon or Fiend (For example, Prince) is an immature demon, normally referred to as a fiend instead as it is much like a teenager phase even if the demon themselves are fully grown and matured. Fiends are the weakest line of demons and tend to exist in abundance.
A Middle Demon or just a Demon (For example, Finley) is a fully realized demon. They tend to be much stronger and rarer than fiends. They could be considered an ‘adult’ and are usually the level of power a demon can reasonably strive to be. However, even just ranking up to a properly titled Demon can be difficult for some.
A Greater Demon or Devil (For example, Dwi) is at the top of the food chain in Hell. Their powers, appearance, and abilities can vary vastly from one to another, but no Devil is something to sneeze at. They have the ability to rule over other demons with their “marks”.
A Nephilim (For example, Deadeyes) is a type of celestial that lives completely outside of the cycle. They are born from the mixing of an angel and demon and are something completely new and very powerful.
While each step might not necessarily lead to another step, almost all parts of the celestial cycle can transition to something else or were something else in the past.
Some changes are reversible, but most are not, and there are many different paths an individual celestial may take; one could start as an angel and end up a devil, a mortal may be blessed with celestialhood, an imp could grow into a fiend that rises to be an angel, or a fallen angel might lose their spark and become simply mortal.
Celestials may also be created or in some cases born, and they may also die, but death means something very different to immortals than it does for mortals.