Battle of the Quarantine Zone
From Halopedia, the Halo wiki
Background info
One of the few four-sided battles of the 9th Age of Reclamation, the Covenant and UNSC fought through the Quarantine Zone to look for the Index, the Sacred Icon by the Covenant. They had to go trough massive numbers of Flood and Forerunner machines: Sentinels and Enforcers.
Battle
The Arbiter was sent to the surface of Delta Halo to retrieve the Sacred Icon. After he lowered the Containment shield, the Flood was able to walk more freely round the Ring. The Humans of the In Amber Clad that were searching for the Index were surprised by this and most of them were assimilated by the Flood, enlarging their numbers. The Flood did not only assimilated the Humans but they learned to use their vehicles as well: Scorpions and Warthogs. The Covenant warriors who were sent to retrieve the Index were assimilated as well by the Flood. With this, the Flood had even more vehicles: Wraiths and Ghosts. Besides all of this, the Arbiter and his squad of SpecOps Elites were able to battle their way trough the Flood and Sentinels. They regrouped with Rtas 'Vadumee and followed the Humans with a gondola that was headed towards the Library.
Library
Once the Arbiter and his squad arrived at the Library, the Humans were already inside. The Arbiters squad of Elites were left behind to guard the gondola since it was their only way out. The Arbiter found the Humans (Miranda Keyes, and Sergeant Johnson) who retrieved the Index seconds before the Arbiter arrived. The Arbiter knocked out Johnson and before he could get to Miranda Tartarus showed up and using his Gravity Hammer knocked out Miranda and took the index from the Arbiter and blasted him off the edge where the Index was stored, letting Tartarus think that he was dead.
