Mentus was a Spaceknight storing the dark side of the Prime Director of Galador. The Prime Director of Galador during the time of the Dire Wraith invasion felt guilty for retaining his humanity while he asked Galador's youth to give up theirs to become Spaceknights and defend the planet. He attempted to to create a Spaceknight by a new process. Instead of bonding a human to an armor, the human would control the armor by sheer force of will. However his darker side and suppressed evil urges were the only ones passing and animating the armor, creating Mentus.
Mentus escaped his creator and went into hiding, plotting to take over Galador. He witnessed the sentencing of Terminator to death and rescued the Spaceknight. He mentally enslaved Terminator to his will. He assigned Terminator to destroy the human bodies of the Spaceknights, held in storage and awaiting their return. Terminator resisted the order but stole the body of Rom, a Spaceknight hated by him. Mentus changed his plan and bonded Terminator to the body of Rom, also changing the armor to be an exact duplicate to that of Rom. Also providing Terminator with identical equipment to that of Rom. He poisoned the Prime Director and then had Terminator pose as the returning Rom. This "Rom" announced the Dire Wraiths to be dead and the war to be over. The Galadorians soon appointed "Rom" as the new Prime Director. Mentus becoming the power behind the throne. The original body of the Prime Director was placed in suspended animation in case Mentus returned to human form.
Mentus had to deal with a flaw to his plans. The real Rom was still out there. Mentus signed a pact with a number of Dire Wraiths, having them lure Rome to Galador. There Mentus attempted to capture him, as he had already captured other Spaceknights. However Rom managed to free himself and the various captives. The released Prime Director reabsorbed Mentus into his psyche. The Prime Director found himself becoming a disembodied consciousness. He attempted to communicate with the arriving Galactus but was absorbed by the Devourer.