Karth Arn was an android from the 30th century, created by Dr Mar Londo to explore the risky underground of Zuun and extract the mineral zuunium than only existed in that world. After battle the dangers from the zuunian, Karth, thanks to his greater intelligence, was the only android capable to survive to return successfully with a load of the mineral.

However Karth grew jealously when he saw how the Dr. Londo gave more attention to his next experiment: use the zuunium to gave his son, Brin , superpowers. He was frustrated to see how his creator had eyes only to his son, but he still was loyal to the scientist. That changed but when the dr Londo suddenly died before finished his experiment, he knocked Brin and mindwashed him to convince than Karth was the son of Londo and Brin was the android. Karth then wanted Brin to work for him as a living tool. But the confused Brin, fighting against his conditioning, run away searching himself and wondering about his (supposedly) artificial existence.

The deception was uncover when the Legion of Super-Heroes tracked the origin of Brin to the planet Zuun, where they exposed the lies of Karth, who confessed his crimes and revealed the origin of Brin.