A Kryptonian refugee and exiled citizen seeking to steal the super-powers of surviving Kryptonians in order to replace his own absent powers.
Originally, Klax-Ar destroys his super-powers through exposure to atron-rays. He travels to Earth and attempts to transfer Superboy's powers to himself but the Boy of Steel tricks him by sending one of the Superboy Robots with Klax-Ar to outer-space in his stead. (SB No. 67/3, Sep 1958: "The Man Who Destroyed Krypton!")
Later, Klax-Ar short-circuits the Superboy robot and uses its parts to construct a space-sled. While in space, Klax-Ar sees Supergirl while she was traveling to the prison planet Kronis, and attacks her with the space-sled and his Mentomatron helmet. However, he is once again defeated when Supergirl leads him into the polluted atmosphere of Earth, which makes it impossible for Superman's robots to function, and, since the space-sled has been constructed from parts taken from the Superboy robot, renders his sled useless by effectively destroying the robot's delicate circuits. Supergirl then kicks the useless sled to Midvale (SF No. 187/6, Jan/Feb 1978: "Birthright of Power!").