Origin
Guy Gardner with the help of G’Nort stops the Quadian plot and Thoom looses his power ring. Thoom will eventually become a security agent for the Palindrordnilapians. They send Thoom, Boom and Buk-50 to earth to test Guy to see if he would be a worthy leader of security agents for the Palindrordnilapians
Creation
Thoom was created by Gerard Jones for use in DC Comics. His first appearance is in Green Lantern #11 which was released April of 1991.