Selune is a goddess said to live on one of Celestia’s three moons (The Three Sisters). The moon itself has the same name and she is the embodiment of it. However she has apparently been ‘summoned down’ to Celestia on a number of occasions, which makes her a bit different from the other two. She can choose to look rather humanoid, but that is not her only form and so she is often called ‘The goddess of Change’. Probably all the more fitting for the fact that the associated moon goes through a series of changes among the heavens and can even change color during the year.
What no one knows about Selune is that she is in fact an orbital defense platform setup on the moon of the same name by the ancients. She is a nanite framework around an AI core, which can build and modify itself from the materials around it to reshape and reform into all sorts of things. It also allows Selune to regenerate. In a purely Celestian view Selune truly is a Goddess as nothing they possess could truly harm her and on the other hand she can form the firepower needed to raze any city in a single shot. Thankfully compared to most other AI’s from that period she was not corrupted and is more or less sane. The only oddity she seems to show is a desire for her ‘builders’ to worship her, though worship may be to strong a word for what she actually wants from them.
Her contact is limited to the activation single from repair centers she is keyed to, some of which still function and cause her to return to Celestia for ‘maintenance’. That maintenance was supposed to be done by the original races and not automatic machines, so it has been millenia since her last real maintenance. However she is bound to those maintenance signals and so returns every time one summons her. At this point it is only a matter of time until someone pulls apart a communications station and ends up with a maintenance beacon in their hands that could summon Selune. The problem then becomes what will happen when she can be summoned at will, She isn’t likely to like being called down to Celestia very often and even if she did agree to help someone with a beacon the results may not be what they would hope for.