After a long time of being trapped, Pinkamena finally breaks out of the mirror prison. Discord sees her as a source of chaos, and makes her an alicorn with only chaos and death magic. And with her new powers, she plunges Equestria into chaos.

Why did Pinkie go insane, and turn into Pinkamena? It all goes down to pegasus pony from Cloudsdale; Surprise. After she came to Ponyville, she started to replace Pinkie. Even the mane 5 seemed to replace Pinkie. It wasn't long until Pinkie snapped..