From Titans

Everyone is searching for Mason. A sparkle of hope arises when Eris, the goddess of Chaos, sends an invitation to her wedding engagement party. She���s holding Mason hostage, and Skylar and her friends only need permission to enter Eris���s world to rescue him. Eris not only sets up a hunt in the Labyrinth of Crete, but makes a bargain with the Titans she rescued.