It was the cause of the oath "A Zeus and Poseidon kid vs a Hades kid, during WW2" (I forgot what the actual thing said, pretty sure that is close).
Also, the op's name sparked me a question - has anyone read the lunar chronicles? (I love it).
YOU ARE READING
Percy Jackson Tumblr Post and Others - Book 2
FanfictionThis is the second book. Read book 1 first. Literally what the title says.