Eclissi was born on the moon. He was born to a certain evil tyrant hell-bent on returning to the planet and claiming Equestria for her own. Eclissi was left behind and subsequently forgotten about.

Now, five years later, Eclissi has deciphered the very magic that Celestia used to banish her sister to the moon and has banished himself to Equestria. Now, he's out for revenge.

But how does one get revenge on their mother for forgetting their child on the moon?

(I'm aware of the story of Nyx, but I've never read it. I've got a general idea of what it's about so I'll do my best to avoid similar themes in this.)