You do not know

The supernatural presence in this dystopia is founded on the notion that there is a reason that archetypes have prevailed through all of human mythology. After all, many religions have some similarity in themes, storylines, creature personalities, magics, and roles in the way that the world functions (see: comparative mythology). Here, we take this to mean that no single culture got it right. There are countless incorporeal beings that have thrived on the planet for eons. Each entity appears as a distorted hybrid of at least 2 or 3 mythological etiologies-- precisely because these myths were derived, over-simplified and sometimes inaccurately, from these creatures.

Avatars tend to wind up choosing people who had some genetic ancestry indigenous to the culture where their mythology took root, however long ago. However, this is far from a rule, and given the amount of interracial relations common in the world now, this is only a guideline.

Their personalities are not human, but there is enough individual variability that they might as well be. Most are so old that they experience their human connections with terrifying, inexorable patience and very little sanguinity; in a sense, there simply isn't enough time in a human's existence to develop a real connection. However, those that possess a person have some motivation to do so, whether it's to: help, harm, explore what being human is like, relieve existential ennui, manifest their own inarguable cosmic purpose, or that they hope fate will cross their mortal instrument's path with another avatar in the interest of vengeance.

However, one thing is apparent for all avatars: humanity looks like it's on the edge of extinction.

Unlike the power sets typically favored by comic books, mythological creatures and figures often have a surprisingly diverse and folky array of powers. Zeus may be typefied by lightning and physical prowess and weather-related drama, but he was also a shapeshifter and could control animals.

Individuals who are possessed are granted abilities associated with their avatar's abilities. These generally manifest as psionic versions of the original magic, but rules may vary depending on the individual's psychology or their avatar's fickle idiosyncrasies. Foci objects or incantations may well be necessary for some to activate their abilities.