Ghost

Sergeant "Ghost" served as a Marine within the Hades Corps of the UNSC Corps of Engineers. He was recognized for his cold demeanor and a certain sadism, displaying little to no emotion in any situation, particularly during combat, until the death of a fellow Marine who had asked him to act human for a while.
Ghost was deployed with the Hades Corps to destroy navigation materials and prototype weapons during the Battle of Algolis, in accordance with the Cole Protocol. Initially, it seemed he had disobeyed orders to destroy a set of prototype powered armor by entering the battle wearing it. However, he maintained that he was fulfilling his duty by utilizing the remaining time before the suit's self-destruct sequence to provide cover for the extraction of Marines and civilians from Algolis.
Ghost is the main character in "Prototype."