J. Finn also known as T9581, was a naval officer turned into a Mutant. He was a former friend of John Bishop.
It is shown that Bishop was at his wedding, and that he had a son. After he was turned into a monster, the Purple Dragons steal weapons from Bishop, including T9581. At the Purple Dragons' lair, T9581 attacks Hun, and then Leonardo and Casey Jones. He then tries to retrieve the woman he married, but Bishop and his men find him and attempt to get him under control. An explosion occurred during the struggle, presumably killing the monster. T9581 is then seen swimming in the sea, and remembering his wedding.