Raid on the Threshold gas mine

The Battle of the Gas Mine took place during the Ninth Age of Reclamation. It was an attempt by Covenant SpecOps forces, under partial command of The Arbiter, to eliminate the Heretic leader, Sesa 'Refumee. Sentinel forces on the installation apparently sided with the Heretic forces, presumably due to 343 Guilty Spark's presence there. The Flood later joined the battle, possibly due to the carelessness of the Heretics. All Flood and Heretic forces (excluding Guilty Spark) are presumed destroyed, due to the destruction of the installation.

Sequence of Events
Sometime after the Battle of Installation 4, the Monitor (343 Guilty Spark) arrived at a Foreunner Gas Mine. There, he met the Covenant search team, lead by Sesa Refumee. Refumee, learning of the truth of the Halos, inspired rebellion and led his team in a Heretic Campaign. His team holed up at the mine, fortifying it with Shielded turrets, Banshee aircraft, and Anti Aircraft Fuel Rod Guns. They dressed in the armor of the Elites homeworld, and armed themselves with Needlers, Carbines, Fuel Rod Cannons. 343 Guilty Spark reinforced these defenses with Sentinels and intelligence. Here, the Heretics lashed out at any Covenant assault team that came near.

Around this time, the disgraced Fleet Commander was given the Prophets blessing and led a Spec Ops team against the Heretics, as the Arbiter.