The timeline has been altered. Celestia and Luna are gone, the Elements of Harmony are inert and the Element bearers have fractured, dispersed to follow their own beliefs, their own agendas, and avenge their own betrayals.
And none of that has a damn thing to do with the Crystal Empire.
King Sombra has emerged, unchallenged, to find himself in a world completely different from the one he remembered. A world that is dark, a world that is savage, a world that is unforgiving. A world he thought opposite to all the qualities he represented and now seeks to outdo all he ever accomplished.
The dark tyrant is not pleased, but the dark tyrant has bigger problems to deal with; with Celestia gone nopony remembers him, nopony knows him, and in that ignorance nopony fears him.
Other powers have arisen, kingdoms with their own myths, their own beliefs, their own tyrants and their own monsters...