Jinku was the Witch-Doctor of the Lava Men. When an explosion from deep within the Earth rocked the realm of the Lava Men, the Lava Men learned that it was caused by the Living Rock that forced its way into their subterranean territory. The Living Rock would generate explosive force when struck, and it would continue to grow in size until it exploded. Jinku counseled King Basallo to build a machine and drive the Living Rock to the surface world where it would destroy the surface of the planet instead. Despite the protests from Molto, their supreme warrior, the King agreed and followed Jinku's recommendations. This brought them into a conflict with the Avengers, during which Jinku used his radioactive rod against Thor's Hammer - causing Thor to unwittingly transform into Donald Blake mid-combat. This unexpected event scared the supersticious Jinku away. The battle ended when the Avengers duped the Hulk into striking the Living Rock in the one spot that would destroy it and threatened to destroy the Lava Men should they keep with their conquest ideas. With the threat over, the Lava Men returned to Subterranea.
Some time later, Jinku had a vision in his dreams promising to lead his people to conquest. Unbeknownst to Jinku, this dream was actually caused by They Who Wield Power for their own purposes. Nonetheless, Jinku convinced the King to steal the Mole Man's volcano-activating machine from the Moloids. The machine lacked a power source, and Jinku sought to obtain Mjolnir, the hammer of Thor, as that source. To this end, he ranted of his plans to destroy humanity in front of Molto, who he knew would inform Thor, causing him to investigate. Jinku followed Molto and blasted him, mortally wounding him, but not killing him instantly. Molto made his way to the surface world where he encountered the Human Torch, whom he initially mistook for an agent of Jinku, but then convinced him to summon Thor. After relating his story to Thor and the Torch, Molto died, and his body disintegrated (as all Lava Men do at death). But his warning enabled Thor and the Torch to stop Jinku's plan.After the Lava Men's demon patron Cha'sa'dra was killed by the Avengers during Inferno Jinku created a new race of Lava Men to attack the Avengers. Jinku blamed the Avengers for the real Lava Men turning to stone. It turns out the Lava Men's stone skin was a chrysalis stage turning them into beings made of gold. Jinku's lava skin fell off and he too had a golden form. He made peace with the Avengers and left with his people.
The golden forms were temporary. When Jinku later attacked X-Force he and the Lava Men's forms had become more monstrous than before.