As a slave, Hiro-Kala waited for the death of his master, Axeman Bone, so that he may be set free. He thought his liberation would come in the form of Skaar, son of the Hulk, but that was not to be. The axeman was indeed injured, but not fatally. Hiro-Kala sought to finish the job on his own but was convinced to stay his hand. Believing he could stop the warring ways of the axeman, Hiro-Kala fled. Enduring the harsh desert alone without food or water, Hiro-Kala faced barbarians and tamed feral beasts - proving there was more to him than even he knew. He traveled to the battlefield where Skaar defeated Hiro-Amin, a shadow priest who wielded the Old Power. Confessing he wanted the power for himself, Hiro-Kala killed Hiro-Amin with Axeman Bone's weapon in the hope the Old Power would be transferred to him. Even though it was not, the journey wasn't a complete loss for the axeman granted Hiro-Kala his freedom and gave him his name.
When Skaar drew the Old Power into himself, he immediately began to abuse it. Hiro-Kala could somehow hear the voices of the old ones, even Caiera, and told Skaar he was killing his mother all over again. Skaar only cared about wiping Sakaar clean – a task that would soon be done by the world devourer, Galactus. Skaar set out to kill Axeman Bone and freed many of the axeman's slaves. When Hiro-Kala was asked to show his loyalty, he spit in Skaar's face and refused to follow. It was at that moment, Hiro-Kala began to emerge as a leader, and those who stayed behind with him decided to follow him. When Galactus finally arrived, the death of Sakaar was imminent. Caiera's spirit drew upon the power which was once hers and activated the stone ships of her people, evacuating as many as she could. When it appeared as if Hiro-Kala's vessel would not be able to avoid a disastrous end, he summoned the might to claim his birthright. Hiro-Kala, surging with Old Power, confronted Galactus and left him with a warning. Galactus did not even notice his passing, but Caiera finally acknowledged him as her son. Once back aboard his stone ship Hiro-Kala assumed command and brought his followers to a violent world called Giausar. In order to send a message to Galactus, Hiro-Kala waged war against the planet's inhabitants, despite his mother's pleas. Growing colder and darker as the days progressed, Hiro-Kala was betrayed by his own people in hopes of saving Giausar from destruction. Princess Omaka and Old Sam were dealt with harshly for their disloyalty. Nearing the complete breakdown of the planet, Hiro-Kala finally got what he was hoping for all along – the coming of Galactus. He tricked the planet-eater into believing he was offering Giausar to him as tribute, but in actuality, Hiro-Kala poisoned the world with his war and by combining the Old Power with the Power Cosmic. The result was nearly fatal to Galactus, and the son of Hulk went so far as to threaten the world-devourer that the next time he ingested any planet teeming with Old Power, it would be the end of him. Caiera came to Hiro-Kala one last time to tell him she now understood he needed to sacrifice a planet to save the universe, and no matter what is said of him, she will always love him for his courage and strength.
Hiro-Kala claimed the Old Power was a blight in the universe and wanted to find his twin brother, Skaar, to purge the Old Power within him. His path was temporarily diverted when Jentorra, niece of Jarella, inadvertently pulled him through the Fault into the Microverse to save her world from the Psyklop. When the hoard of creatures attacked him upon arrival, Hiro-Kala unleashed his fury and destroyed them all. After resurrecting those previously absorbed by the Psyklop, the people of K'ai begged Hiro-Kala to lead them. He declined, instead imbuing some with power to help him rid the Microverse of the Old Power. All the while the daughter of Axeman Bone stayed by Hiro-Kala's side, growing to love him more every day despite the atrocities he committed. Jentorra had been searching for a way to rid her world of Hiro-Kala's presence, and using the Enigma Force Nullifier, Jentorra thought she could kill one even as powerful as he. The Nullifier did not kill Hiro-Kala as intended, but he realized it was a power to challenge his own. The Enigma Force Nullifier found Arcturus Rann and brought him to fight Hiro-Kala, knowing Rann was the perfect candidate to possess its power. As Hiro-Kala was about to unleash the same poisoned energies flowing within the body of Galactus throughout the Microverse to destroy countless planets containing the Old Power, Arcturus Rann severely damaged Hiro-Kala's physical form. While reforming his body, Hiro-Kala came under a new type of attack as Jentorra used magic in attempt to banish him from the Microverse, but Rann told her the Enigma Force could only defeat Hiro-Kala if he remained. Hiro-Kala took control of Jentorra's spell, covering the planet K'ai, and used ancient K'ai ships to pull the world out of the Nullifier's path. Out of danger, Hiro-Kala killed the daughter of Axeman Bone because he understood he was growing to love her as she loved him, and once that happened his powers would be beyond his control and cause the end of all things.
His powers depleted from pulling K'ai through the Fault and into his father's universe, Hiro-Kala was now the target of a grieving father. Fleeing for his life, he searched for a way to recharge his powers before Axeman Bone could enact his revenge for the death of his daughter.