Set in an alternate history where some dark event results in Princess Celestia's untimely demise. No one knows who caused it, but Princess Celestia's death has an immediate impact on Equestria and its people. Luna has transformed back into Nightmare Moon, and blames everyone for Celestia's death. She has declared war on the Crystal Empire, and has posted a bounty for Twilight, the other Mane Six , and Discord. Meanwhile, the other countries notice the power struggle going on in Equestria, and each of them see it as an opportunity to gain Equestrian Land. It's up to Twilight and friends to stop Nightmare Moon and bring peace back to Equestria in what could be considered their most dangerous mission yet.