When the old Gods saw greatness, wisdom or the potential for important learnings in a narrative, they placed it in the skies in the form of a constellation. Though many of the stories have been mostly forgotten, the Gods left a gatekeeper in place on Earth to make sure that if nothing else, the star patterns stayed where they were, locked in the heavens.
Mona has roamed the Earth for thousands of years. She's died and been reborn several times, though each rebirth comes with a memory latency that leaves her remembering details rather than chronological storylines. She is, after all, busy remembering the stories of old which are, honestly, far more important than keeping track of her own existence - eternal, as it is. Even so, Mona remembers (vaguely) the scent of fire smoldering in icy caves; she remembers more clearly the stench of the streets, the rats and - unfortunately - more than a few executions of the middle ages; the smoke from burning houses and villages, wars fought and lost; the smell of Versailles, oh, quite...
Usually, she likes to pretend that she's in it for the people. The human race really is her favourite and she does her best to blend in amongst them, to live like they do (for the most part) and to experience life the way you should when your body comes with an expiration date. Like this, she lives a pretty anonymous existence, keeping track of the heavens and slipping through history, one decade at a time.
That is, when her sweet Millie doesn't burst onto the scene, which does, sadly, tend to lead to murder, mayhem and yet another re-incarnation. For the both of them.~