Kro was born to the race of Deviants, an evolutionary offshoot of humanity, which is cursed with an unstable genetic code causing random physical characteristics to crop up in each newborn child in the race. Kro was born with a number of traits which appear to be unique among the Deviant race and which are beneficial in nature. Chief among these mutations are those granting Kro his longevity and near-indestructibility, both similar to those of another evolutionary offshoot of humanity, the Eternals. Kro was alive around 20,000 years ago at the time that the Second Host of the extraterrestrial Celestials destroyed the Deviant Empire in the Great Cataclysm.
Kro has carefully guarded the secret of his longevity by assuming a series of different identities among the Deviants over the course of his extraordinarily long life, using his powers to alter his facial features to complete his disguises. Kro fears that if he allowed the other Deviants to know that he was virtually immortal, they would subject him to genetic experimentation in order to try to learn how to duplicate the mutations that gave him his near-immortality in themselves. Kro has studied the arts of warfare throughout his life and has often led Deviant armies in his various guises. Currently Kro uses the same name and facial features that he did thousands of years ago. He claims to be a descendant of this "original" Kro.
, the King of Comics, created Kro in his first appearance in the Eternals vol 1 #1
(7/1976). In a retcon revealed in Marvel Universe #7
(12/1998), the Roman god Pluto that appeared in Red Raven Comics #1 (8/1940) and in Captain America Comics #1-3
(1941) was Kro in one of his disguises. An interesting coincidence, Jack Kirby was the artist for Red Raven Comics #1 and Captain America Comics #1.
In Kro's early years, Kro fell in love with Thena, daughter of Zuras, ruler of the Eternals of Earth. Thena returned Kro's love, but their relationship, perhaps the only such liaison between the two divergent races of humanity, which have long been enemies, ended badly. Kro and Thena parted, although they retained strong feelings for each other. Thena assumed that Kro eventually died, and was surprised when she encountered him again in recent years. Kro attempted to renew their relationship, but failed.
During the 1940's, Kro battled Makkari while using aliases such Rudolph Hendler, Pluto, Paul Sayden and Satan. In the 1950's, he oversaw the unleashing of Deviant mutates such as Tricephalous, Giganto, Gigantus, and others from Monster Island, near Japan.
After the demise of Zuras, Brother Tode, the monarch of the Deviants, led an assault on Olympia, the principal city of the Eternals, where the Deviants captured and imprisoned all the Eternals. Almost the entire Deviant ruling elite, including Warlord Kro, accompanied Tode and Deviant troops on this venture. Thanks to the intervention of James Rhodes as Iron Man, the Eternals regained their freedom and captured the Deviants that were on Olympia. The Eternals decided to transform all of the captured Deviants into a large block of atoms and send the block into outer space. Before the Eternals carried out this plan, Thena secretly released Kro from his cell, and Kro escaped. Shortly thereafter, most of Earth's Eternals left for outer space. Thena became the ruler of the Eternals left on Earth.
Kro made his way back to the Deviants' city in undersea Lemuria, intent on making himself their monarch now that virtually the entire Deviant ruling class was no more. To his astonishment Kro discovered that the Deviant priesthood, headed by the priestlord Ghaur, was maneuvering to become the true ruling power in Deviant Lemuria. Since one of the priesthood's roles was to designate the new monarch, Kro confronted Ghaur and made his wish to become king clear. Ghaur allowed Kro to become monarch, but continued to pursue his plans. He had Kro lead an expedition to the Pyramid of the Winds, an Eternal structure in the Arctic, to retrieve a mysterious vial. Ghaur apparently hoped that Kro would be killed by the Eternals in the course of this venture. Once Kro found the vial, a Deviant priest and his guards demanded he give it to them, but Kro, determined to maintain his authority as ruler, refused. A party of Eternals led by Ikaris arrived, and Ikaris fought Kro for the vial. Thena, still in love with Kro, prevented Ikaris from killing him, and, on Kro's request, teleported Kro away. The Deviant priest's guards had managed to get hold of the vial for their masters. Kro and Thena traveled together as renegades, each hunted by his or her own race. They were finally found by Ikaris, who let them go after he replaced Thena as Prime Eternal. However, Ghaur still seeks to capture Kro.
At this time the current whereabouts of Kro is unknown.
Despite his Deviant heritage, Kro possesses a number of superhuman traits characteristic of an Eternal. Kro maintains a virtually unbreakable mental control over the processes and structure of his body even when he is asleep or unconscious. As a result, Kro has a lifespan that has already lasted over 20,000 years and is immune to disease and aging. His mental control over his body enables him to maintain a youthful, vigorous physical condition. Kro is not as nearly indestructible as the Eternals. (For example, Ikaris nearly killed Kro once by strangulation.) But while sufficient force can kill Kro, he can use his mental control over his body to heal himself after being injured.
Kro also possesses the power of physical malleability, which is atypical for a Deviant. At will he can cause most of the tissue of his body to become pliant, enabling him to shape it mentally like putty into different configurations. Once the tissue is set in an altered form, Kro has only to stop concentrating and his body will retain that shape until such time as he concentrates upon changing it again. This ability enables him to disguise himself and take the appearance of others (with cosmetic help for skin color, body hair, and so forth). One of Kro's favorite ploys is to pass himself off among ordinary humanity as a demon by fashioning horns on his head.
However, Kro's shape-changing powers are limited. He cannot alter the shape of his skeleton in more than minor ways. Moreover, he cannot eliminate any of his mass while transforming; he can only redistribute his 320 pounds of weight. Hence, he usually only uses his shape-changing power to alter his facial features. He can mentally mold the shape of his skull somewhat.
Kro has about three times the physical endurance of an ordinary human athlete. His heart is not located in the same place as an ordinary human being's; its true location is unrevealed.
Kro is a master military strategist, a superb military commander, a good hand-to-hand combatant, and an expert in the use of Deviant weaponry.
Kro can lift (press) around 800 lbs. (Most Deviants are not physically stronger than ordinary human beings, although there are indeed many superhumanly strong Deviants.)
Kro frequently wears special glasses designed to extend his vision into the infrared and ultraviolet ranges. Hence, if Kro is wearing these glasses in a room where there is no visible light, he can still detect objects by perceiving the heat (infrared radiation) they give off.
Kro has employed a number of weapons developed by Deviant technology. Among his favorites are flame-guns, vibro-whips, and shroud-guns. Once while battling Ikaris Kro wore gloves from whose fingertips he could project vastly powerful force blasts which could not injure his virtually invulnerable Eternal foe but which caused Ikaris intense pain.