The planet K'ai is located in the Microverse, also known as Sub-Atomica.
The race inhabiting K'ai are a blonde haired, green skinned humanoid race. The planet was once ruled by Queen Jarella, who eventually formed a romantic relationship with the Hulk, who none of the people feared as the Hulk shared similar physical traits to them.
The mystics of the planet long believed that the Hulk was their savior and would use incantations to summon the Hulk to them in time of need. The queen's niece Jentorra once tried to summon the Hulk, but instead summoned his son Hiro Kala. With his great power, Hiro saved the population and became revered as their new ruler.
Jetorra uses a magical spell against Hiro Kala, but he uses it for his own purposes, transporting himself and the planet out of the Microverse. After this, Hiro finds the planets Worldmind, the sentient state of the planet itself, that explains it is dying from leaving the Microverse. The Worldmind gives Hiro some of it's own power and the War-Mind in exchange for some of his Old Power. This power is used to sustain the planet and restore its life and habitability.
As his father once was, Hiro became the king of K'ai.