Rex is normally happy and lighthearted, not really caring about whatever happens to him. He usually depends on others for help, as he lived a very sheltered life. He has shown to be very caring to those he's close to, like Shnee, Desmond and Lyss. He does not care much for his own safety or well being, as long as those he cares for are safe. He carries a great burden from his brother's death, and the goal to carry on his mission, which causes him to be quiet and serious at times. He was willing to sacrifice himself for Desmond's sake, and threw a brick at the mutant dog to protect Shnee.