The Reapers are invading Equestria, intent upon destroying and enslaving the upstart ponies before they can affect the rest of the cycle. Unfortunately for them, Luna stands in their way.
The rebels planned things well. They've broken through and Celestia is the only one left between them and the throne. Now all they have to do is take it.
Only a few hours after the Griffon Empire declared war on Equestria, Princess Celestia waved a white flag and asked for an audience with the Griffon Emperor. The Emperor thinks she's here to negotiate Equestria's surrender. He's wrong.
A Reaper dreadnaught confronts Celestia, intent upon indoctrinating the leadership of the ponies. Said Reaper quickly learns exactly why Celestia has earned the title Unconquered.