What is every villain that attacked Equestria was corrupted by some sort of evil shadow? Even the shadow king was corrupted by this. King Sombra, Nightmare Moon, Queen Chrysalis, and Lord Discord were all corrupted by this. None had the intention of attacking and trying to take over the world. some were simply just looking for friends, others were trying save kingdoms, and another just wanted to reconized for what she was good at. Together, they have to destroy the evil that corrupted them and save Equestria.

Sidenote: This has nothing to do with Trixie. It was just be best picture I could find on Google. Princess Celestia is also a main character. I couldn't add her though.