After a company of Equestria's soldiers are massacred, Twilight and her friends learn of an ancient evil banished by Princess Celestia and Princess Luna centuries ago has escaped and is seeking revenge against Equestria. Thinking of it as nothing more than just another challenge, the ponies gear for battle, only to discover this evil is unlike anything they've ever encountered. Outmatched and outsmarted by this remorseless and savage enemy, Equestria soon begins to burn and when conflicting interests begin to divide them, all begins to collapse for the mane six. Twilight must muster all her knowledge and with the help of a troubled soldier who seems to know a suspiciously large amount about the enemy, Twilight learns lessons she never bargained for, including that a fine line exists between what makes someone your friend or your enemy.