(Warning: massive spoilers for the MLP Movie and "Kid Icarus: Uprising")

The Storm King is defeated, Equestria is saved, and all of the allies made have gone their separate ways to live their lives free from the tyrant's rule. Everything should be alright... except Twilight Sparkle is haunted night after night by dreams of her own actions. Actions that almost caused a rift between her and the ponies she holds so dear, leading her to question her worth as the Princess of Friendship.

Meanwhile, in the world of Angel Land, a returning threat has begun to arise. After a decade of Palutena's Army and Viridi's Forces of Nature fighting over humanity's right to live, the Underworld Army has returned to resume what they started: the killing and consuming of human souls. However, they've set their sights upon a new world: Equestria itself.

Upon realizing this, the two warring armies must quickly band together yet again to stop this threat and save this new world. Together, both sets of heroes will learn what friendship really means, and Twilight will understand the true essence of her role as princess.