She's a work in progress, but I wanted to share my idea so far. She's how (In my headcannon/opinion/in no way fact) I imagine Celestia and Luna's mother to have looked like. I mean there's a lot of Greek mythology in MLP and that gave me some inspiration for this pretty mare. I'm still tweaking her design, and how I want her to look, but this version of her here was just too pretty to ignore. I may keep her around as a character in another universe, though for my personal headcannon Gaia was the first equine in Equestria who had control over the earth she stood on. Other ponies and horses and such existed but didn't have the magic she did. At some point she met Uranus who I imagined to be the first Alicorn (Though lacking any magic an Earth pony of today would have) and they somehow took reign over Equestria. It's not a fully fleshed out idea, and I'm not much of a writer, but in the end they would have created Celestia and Luna before they passed on. Leaving the two princesses in charge, and because they still believed their parents to be the true king and queen never took on the title of queen themselves.
...Like I said, I'm not much of a writer, I just come up with shizz while I draw, and after 10+ hours you'd think I'd have a better story in mind for her.