Castor said that the Golden Bough Legion is investigating the secrets of the Eracus Temple Cavern, and he told you to go to Axelion for a special mission. You restored the walls of the spiral towers in the temple as Axelion asked, and saw a message to a child called Kahrun. When you reported this to Castor, he deduced that the Eracus Temple Cavern wasn't actually a temple but an ancient playground.