 Voice actors returning to reprise their roles in Halo 3 include Jen Taylor as Cortana , David Scully as Sergeant Johnson and the Elites , Keith David as the Arbiter , Tim Dadabo as 343 Guilty Spark , Ron Perlman as Lord Hood , Robert Davi as Rtas ' Vadum , and Steve Downes as the voice of Master Chief . The game also features new voices , with Terence Stamp and Justis Bolding replacing Halo 2 voice actors Michael Wincott and Julie Benz as the Prophet of Truth and Miranda Keyes respectively . Additional voices include celebrity presenter Jonathan Ross , Nathan Fillion , Adam Baldwin , Alan Tudyk , Katee Sackhoff , and John DiMaggio . Members of the Halo machinima Red vs. Blue ( Burnie Burns , Gus Sorola , Matt Hullum , Jason Saldaña , Geoff Ramsey , and Joel Heyman ) have a cameo role . 
