In the Marvel Universe, Kro is a military leader and sometimes acts as the leader of the Deviant race, an evolutionary offshoot of the human race created by the Celestials. He is one of the first Earth Deviants created. Besides being a shapeshifter, he is immortal. He hides this from his fellow Deviants by pretending to be a long line of fathers/sons. Also hidden from the Deviants is his long-standing (100,000 years) on-off relationship with Thena, leader of the Eternals and mother of their twin children, Donald & Deborah Ritter. This relationship unravels during the course of the story.