Kro is a leading member of the
Deviant race, an evolutionary offshoot of humanity 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 his own descendant. 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 and Deborah Ritter. Their relationship later unravels. In the advent of the Heroic Age, Kro attacks New York, trying to incite fear in the human population of the incoming Celestial judgement. He battles the Eternals and agrees to a truce with Thena, showing themselves to the modern world. Kro tries to reconcile with Thena, bringing her to
Lemuria. Thena is treated as royalty, but becomes horrified with many of the Deviants' practices, including their gladiatorial fights to the death and killing of Deviants with more monstrous appearances. Thena flees Lemuria with the gladiators
Ransak and
Karkas, angering Kro. After the death of Deviant aristocrat Brother Tode, Kro returns to Lemuria and became a figurehead monarch for the Deviants. He enters a power struggle with Priestlord
Ghaur, who decides to take power
de facto. Kro attacks the Eternals once more with his giant armada. However,
Ikaris and
Makkari defeat the Deviants. Kro is betrayed by agents of Ghaur and escapes. Kro joins Thena in fleeing from the Deviants and the Eternals. Finally, Ikaris finds them and replaces Thena as Prime Eternal after a ceremony. Ghaur tries to take the power of the
Dreaming Celestial, but is stopped by the
Avengers and Eternals. After the disintegration of Ghaur, Kro remains as the leader of the Deviants and agrees to a truce with Ikaris. Some time later, Kro locates Thena and her twin children, Donald and Deborah Ritter. Together, they end the tyranny of Brother Visara in Lemuria and join as a family. Kro is also the founder of the Deviant team Delta Network, including some heroic Deviants like Ransak, Karkas and his own children. He led them in an attempt to rescue the Avengers from Ghaur. Much later, a plague devastates Lemuria, rendering all male Deviants sterile. A power struggle between
Ereshkigal and Ghaur ensues. Ghaur wins and promises the Deviants that they will have their fertility restored with the help of the kidnapped Eternal
Phastos. Kro is acting in the sidelines as general and attacks Olympia, bringing the Eternals' resurrection machine and Phastos to Lemuria.
Thor rescues Phastos and battles Ghaur. Kro activates a stolen Asgardian Unbiding stone, which threatens to destroy the universe. When Thor destroys the stone, Ghaur and Ereshkigal disappear and Kro is left to lead the Deviants. He regrets the incident and tells Thor that he has abandoned his ambitions. ==Powers and abilities==