Did you ever hear the tale of Darth Luna The Wise?

I thought not. It's not a story Celestia would tell you.

It’s a pony legend. Darth Luna was a Dark Lord of the ponies, so powerful and so wise she could use her magic to influence the moon to create night… she had such a knowledge of the dark side that she could even keep the night she cared about from ending. The dark side of Equestrian magic is a pathway to many abilities some consider to be unnatural. She became so powerful… the only thing she was afraid of was losing her power, which eventually, of course, she did. Unfortunately, she refused to lower the moon, then her sister imprisoned her on it. Ironic. She could save the night from banishment, but not herself.

(The earliest I can find of this is my old post here, but I know I got it from somewhere else, I just can't find it. :/)