Equestria's three villains, Nightmare Moon, Discord, and Chrysalis. Team up, each of there armies ready to attack. Meanwhile, as the Mane six are in Canterlot castle. A strange painting appears on the window. Showing at the top three signs for the three villains. And at the bottom, three more signs with three biped creatures. Then, as the villains try to intimidate them and fly off. A meteor comes crashing through a different window. Showing someone, with a glove and ring on the right hand, a strapped on blade on the left. And a big blue heart in the middle of his shirt. Who is this creature? And why do the signs on him match up to those in the window?

After season 3 if Discord wasn't reformed.

This has three games Involved in it.
Assassin's Creed
Kingdom Hearts
Sonic the Hedgehog