Master Chief Petty Officer John 117 and the Arbiter were once enemies in the Human Covenant War. Master Chief was a SPARTAN II Super Soldier of the United Nations Space Command and the Arbiter was an Elite also known as Sanghelli as well as a former Covenant commander. After the Elites were betrayed by the Covenant leaders, the Prophets, they joined forces with the humans in their campaign in the Ark. After the Prophets and the parasitic Flood were eradicated, Master Chief and Arbiter were in the frigate Forward Unto Dawn. The Slipspace portal did not take the duo back to Earth but to an unknown planet instead.