He was eventually killed by Kakamu, who needed to occupy Tarnok's body in order to prevent his own essence from dissipating.
Tarnok fought in several arena matches on behalf of the Fire Tribe, with Tratus as his blocker.
One day, Tarnok visited the outskirts of Bara Magna's wastelands to look for equipment to salvage. He was spotted by Kakamu, who was searching the surface of Bara Magna for a new body to inhabit - because his previous body had been destroyed, it was only a matter of time before Kakamu would no longer be able to prevent his antidermis from dissipating (which would cause instant death) so he was quite desperate. Thus, Kakamu realized that he had no choice but to kill Tarnok and take his body for his own in order to preserve his life. He killed Tarnok with his Kraata powers and inhabited his form; once that was done, he stripped Tarnok's body of flesh and magnetized nearby pieces of metal to him to prevent his antidermis from leaking out.
When Bara Magna was destroyed, and later recreated, Tarnok was one of the inhabitants who was not resurrected, because he had died before the planet's destruction.