As Camelot basks in peace and prosperity, the dark seeds of destruction are being sown. In the frozen wastelands of the north, men are disappearing without a trace. As King Arthur and his knights undertake a mission into the unknown, they encounter mystical figures, never knowing who they can trust. Morgana is lurking in the shadows, plotting her revenge against King Arthur, enlisting the help of some of those closest to him. With the help of Mordred, Morgana wages war against Camelot. As the battle rages on, Merlin faces his destiny: can he find the strength to save the man he made a king, the Camelot they fought to build, and the brotherhood they shared?