Complex sentence: The group reaches the Sanctuary and they defeat the goblins who possess the Magic Mirror only to be ambushed by Freya, who reveals Sara was using them to find the mirror the entire time.
Split into simpler sentences: The group reaches the Sanctuary and they defeat the goblins who possess the Magic Mirror only to be ambushed by Freya. Freya reveals that Sara was just using them to find the mirror the entire time.