Where did you see him?
You can only get him on the armorgames or sinisterdesign websites, as Dorgon is the bonus teammate from the CD version of TRPG2.
When you win the battle against the Mechanic Captain boss (that be mission 2 part 2), you'll be able to walk around the Mechanics base and you'll see Dorgon: if you click on him and talk to him you'll have a chance of recruiting him as a teammate.
