A creature of old has been present in Equestria since the beginning of the rule of the alicorns, watching, waiting. He saw their fall and the sisters' rise to power. Now, for the first time in eons, he steps from watching and takes action.
Chrysalis has been driven out of Canterlot, her invasion defeated. However, an old friend from her time before coming Queen is more than happy to help her succeed with her plans.