Eldor was a brilliant criminal scientist who escaped from imprisonment on the Prison Planetoid by sneaking into a visiting supply ship. He fled to the world of Antares II, the homeworld of the Protean race, including Chameleon Boy's (then) pet, Proty II. Eldor lied to the native Proteans, telling them he was a descendant of the Llorn, the humanoid race that once lived on the planet and gave the Proteans their shape-changing power. In fact, he only wanted to steal a great weapon that the Llorn had left behind on the planet. However, the Proteans were fooled and so aided him against the Legion, who only defeated him with the help of Unknown Boy, a mysterious hero who later turned out be be Supergirl, affected by red kryptonite.
