Karkaro is the emperor of the Cryog, and the primary antagonist character of the final six issues of Godzilla: Rulers of Earth.
Karkaro resembles the other Cryog, but stands considerably taller than the rest of his kind. Karkaro also possesses dark red skin, in contrast to the others' purplish-blue skin. Karkaro has a circle of horns on his head that resembles a crown, a large frill that extends from his upper body to behind his head, and appears to wear a long black robe with large buttons shaped like eyes.
Karkaro exhibits a twisted sadistic personality that makes Rhizon almost look noble. Karkaro always maintains an air of calm and happiness, and seems to always be wearing a twisted grin on his face. Despite his cheerful exterior, Karkaro enjoys psychologically tormenting and threatening Rhizon, presumably due to some conflict the two had in their past. Karkaro plans to finally conquer the Earth for the Cryog by unleashing the Trilopods, a species of genetically engineered monsters, to completely eradicate all of Earth's kaiju, and then wipe out all life on the planet unopposed.
Karkaro has an unknown past with Rhizon. All that is known is that at one point, Rhizon was Karkaro's most trusted military commander before an incident occurred that apparently caused Karkaro's death, leading Rhizon to assume command of the Cryogs' forces and attempt to conquer Earth. Karkaro was not actually dead, but blamed Rhizon for betraying him and the Cryog race, and followed Rhizon to Earth, bringing with him the Trilopod hive. Karkaro forcibly boarded Rhizon's ship and took command of it, essentially holding Rhizon prisoner. Karkaro informed Rhizon that he would make him pay for his betrayal, but not after claiming Earth for himself, the planet that Rhizon had tried so hard but failed to conquer. Karkaro unleashed the Trilopods on Earth, and watched in satisfaction as they subdued and captured almost all of Earth's kaiju. Karkaro then sent the Trilopod hive to Los Angeles, intending to finally put an end to Earth's resistance.