Christo is an Overlord who is affiliated with a certain giant Netherworld. He is a gifted tactician, and will do whatever it takes to attain victory. Killia's great magic potential caught his eye, and he views Killia as his best shot for assassinating Void Dark. As for Zeroken, he is a young Overlord and self-proclaimed heir of the legendary Great Demon Fist, Goldion. He appears while Killia and the others are fighting the Lost and helps them, even though no one asked him to. He can be stubborn, but has a flexible mindset, changing his attitude depending on who he's interacting with.
Watch the Cristo trailer below.
Watch the Zeroken trailer below.