As of this game, the roster of Iron Guard grew up big. So far, they have Slain and Kregore from Raw Steel, former Metal Guards Barktooth (one of the DM ladder participants) and Karag (one of the customizable bots) who both switched sides to Iron Guard in 2004, and the mercenaries Wraith (member of both SuperNova and the 2004 rendition of the 'Guard) and Blackjack (first member of Supernova, then free agent in 2004). All of them join the returning Harlin and Johnson (the only members of the original 'Guard alongside Lauren) plus several new characters.
Brock not being present in this game alongside Lauren. Consider that the game was launched after Unreal Championship 2: The Liandri Conflict, where they both appear as Necris. It's possible that Brock died before the events of the game.