S1E22 : The Path of Righteousness

Tenma and El Cid are helpless before the combined might of Oneiros and his fellow Dream Gods: Phantasos, Icelos and Morpheus. But Athena appears in the Dream World in order to save Sisyphos; Tenma and El Cid begin the fight anew to protect Athena, and succeed in removing Oneiros from the Dream World, taking the fight into the real world.