You are John-117, the last of the SPARTAN-IIs; a cybernetically and genetically enhanced super soldier. Last hope for all of Mankind, known by the Covenant as the DEMON. You unlock the secrets of the Forerunners, and (with Cortana's help) save all sentient life from destruction and the flood. You are harder, faster, and stronger than any existing soldier in the galaxy. You go MIA after the battle of the Ark and are presumed dead.