When rumors of pony killings reach Ponyville, Twilight writes to the Princess to offer her help. When Celestia fails to respond and Applejack goes missing, the Mane 6 (minus AJ) head to Canterlot. Upon their arrival, Canterlot is in ruins; shops are on fire, the bodies of long dead ponies lie in the streets and whispers come from the dark. "Death lives in the Castle."
The Mane 6 then must work with 2 of their long time enemies, Discord and Nightmare Moon, and figure out who caused this and how to stop them from killing all of Equestria.

First fimfiction, critisizim welcome. (Yes, I do know I suck at summarizing)