Master Eon, the last guardian of Skylands, brings urgent news to a young Portal Master: Hektore has enslaved the Mystic Seekers of the Radiant Isles and forced them to build the Dark Mirror, which he uses to hide the islands from the rest of Skylands and hoard their power for himself. Before Eon can explain the plan, Hektore rediscovers Fargus and his son Wendel—and Fargus sacrifices himself to protect them, leaving Wendel and the Portal Master alone in the Sanctuary, the one place Hektore cannot reach. Their mission: gather Radiance Crystals, rebuild the Shattering Sigil, and destroy the Dark Mirror before Hektore's grip on the Radiant Isles becomes permanent.