Percy swears on the River Styx to return to Calypso when he wins the war, and Zeus was happy to grant the son of Poseidon the wish of exile after the events of the Last Olympian. Now with the threat of the Norse Pantheon and a new prophecy predicting the fall of the Mist, Olympus calls for its greatest hero. Set in MCU Phase 1. Post Giant War. PercyXCalypso.