As an adult, Lex Luthor's driving ambitions are to kill Superman and rule Earth, a stepping stone to dominating the universe, believing a man of his intellect deserves such power. On several occasions he joins forces with Superman's enemy Brainiac (though the two often betray each other as well). Lex is repeatedly imprisoned, but his genius allows him to routinely escape. He also makes it a point to be out of prison on the birthday of Albert Einstein, regarding it as a holiday. A famous non- canonical "imaginary story" from 1961 entitled "The Death of Superman" has Luthor finally succeed in killing Superman after pretending to reform and befriend him.