Rex is a European Lobster who works for the S.A.F. as Gri's subordinate and bruiser.
Rex, quite obviously, looks like a normal Eurpean lobster, except for the armor he wears to conceal his mace.
Rex is sarcastic, with a carefree attitude, but he is quite brutal in battle.
Rex wields a large mace that is capable of increasing in size.
Rex mainly spent his time during Operation Robyen obeying Gri and Messer's orders. He also suggested games of hanafuda to pass the downtime whilst waiting for the outcome of the battle between Stacy's Cousins, whom were brainwashed by the S.A.F. and Perry and his team..