REX Barron the name of the character who is currently Mattrex and leader of the recently-formed Critical Mass, but it is also the online handle of the member who controls him. The same online member is also Saturn on the Cosmic Gladiators, Infinity Mijinion on the Reploid Rebellion and Ride Boarski on the currently restarting Red Alert. He is a relatively new member to the team scene, having first appeared in July 2007.