After major events in their respective worlds, the seven Chaos Emeralds and the six Elements of Harmony collide and cause both Sonic's world and Equestria to go on a collision course! It falls to two speedy blue heroes on the ground and the sky- as well as all their friends- to fix things! But can they do it before both of their worlds are destroyed in the chaos? Piece of cake!

The war between light and darkness is over. Balance has been brought to all dimensions thanks to champions from across universes. They believe the armies of Galeem and Dharkon to be vanquished. They believe the scarred world has a chance for peace. But they think wrong. From the ashes of one war, a new one is set to ignite. And this time, the Smashers will need a little more help.