One is a semi-possessed black alicorn with regrets of his uber-edgy past with an evil corporation, the other is an anti-religion basement dweller (level 8) who never leaves home without his trusty katana and thesaurus, and they are on a journey to travel to the only place they belong.
And the Mane 6 have to put up with both of them.
Thanks to StrawberryP for being an awesome proofreader!