From TokyoPop (based on volume 1):
Imagine a modern-day world in which multiple deities of all religions actually exist--Norse gods roam Asgard, Greek gods rule Mount Olympus, Egyptian gods orbit around Ra, Japanese gods bestow luck and wisdom--the demigod children of these various deities attend the same private high school in Los Angeles! These demigod high school students are the only ones who can stop the plans of the evil gods of several different pantheons who, after seeing their schemes defeated time and time again, have banded together to plunge the world into darkness!
