After Eris' fall, Prince Aster and Celes took power over Equestria, the first being the Moon Monarch, and the second the Sun Monarch, after Aster's discussion with Celes, Nightmare Stallion was created, but, after a failed try to gain the control over Equestria, he was vanished to the Moon.
980 years later, a filly, the Prince Royal Coral, was affected by the curse of Eris, and he became a chimera, he was a shame to the Royal Family of the Northern Seas, so his death was planned, but he became a castaway, after that, he made a great bond with Nightmare Stallion, who led him to a family where he'll find out the great magic that is Brotherhood, a magic, maybe more powerfull than Friendship itself.
Don't Like, Don't read themes:
-Genderbend
-Gay Themes
-The character that should be Twilight Sparke is not par of the main characters, neither any of the Mane Six