His outer appearance is that of a gigantic fish or whale, with what appears to be long fangs, and his body is so resistant to the elements that he can actually swim in subterranean magma lakes. His avatar has the appearance of a large, bald, dark-skinned human male.
Kainen lives on the edge of the mantle layer of the Earth's core, and has a close alliance with Praxis; he is regularly called upon to help relieve pressure from magma pockets by creating levees, which in turn provide near-limitless geothermal energy to the city.When Dr. Will Zimmerman begged the Avatars to stop the tidal waves generated by Kali, Kainen agreed and triggered an earthquake in Pakistan that generated a counterwave to Kali's. The seismic tremors that followed forced the predatory trachnoids that lived in Hollow Earth to migrate to deeper caves, where one of the parasitic queens infested one of Kainen's blood vessels, ultimately causing renal failure. Dr. Helen Magnus and Ranna Seneschal were able perform an emergency surgery to remove the parasite and save Kainen's life.