Sure, she can still fly, but the garbage looks delicious. And everyone's afraid of her! Okay, everyone's afraid of her best friend, too, but her best friend chose to be a banshee.
Then the mysterious Rarity Clan invites her to join. They offer her friendship, and the ultimate secret: how to be turned a second time so that she could choose a different species instead. She could be a werehawk, or a vampire, specter, giant, lorelei, or whatever else she pleases. There's only one catch, and it's a big one.
The tool that's used to do that is a weapon that could destroy the entire city.