The "Gatehouse" Facility

The "Gatehouse" facility was a heavily classified Office of Naval Intelligence research facility located on the UEG colony Avalon. After it's sudden abandonment in 2549 stories and rumours were circulated about the facility's operations. It's history and operations are constantly shrouded in conspiracy and uncertainty.

History
Prior to the settlement of the Avalon colony, the ONI "Gatehouse" facility had already been established, constructed and at least one operation having been conducted within.

Avalon Insurrection
During the Insurrection on Avalon the facility was, to the public eye, an ONI office complex. As such, a local insurgent movement, operating from the nearby rural town of St. Teresa, targeted it for an attack in 2501. The insurgent force left the town however no damage was done to the "Gatehouse". No trace of the insurgents were found and it is suspected they were captured and became lab rats for the facility while ONI incessantly claims no attempt to attack the facility occurred and no insurgents were found. During this time the St. Teresa disappearances were in full swing and it could be assumed that the insurgents suffered the same fate as those who ventured or lived in the forest between the town and the facility.

Human-Covenant War
The facility was at it's operational peak between 2526 and 2549, likely operating to provide the UNSC Navy with advantages over the Covenant. While the actual outcome of the facility's experiments are classified, urban legend and rumours spread by those close to the facility's workers claim that the facility had produced plasma weaponry to be outfitted on the UNSC Ouranos, as well as managing to engineer an alternative to slipspace, creating biological weaponry harmless to humans but lethal to the Covenant and developing a new MJOLNIR armour variant. In 2548 a lone UNSC cruiser under fire reported an unidentified ship appearing nearby, wiping out three CCS-class cruisers with unconventional weaponry before vanishing. The surviving crew of the UNSC cruiser disappeared in the following months.

In December 2549 St. Teresa was evacuated as the facility went into lockdown. A platoon of UNSC marines were deployed in M831 Troop-transports supported by a wing of AV-14 attack VTOLs and one M850 Main Battle Tank. The following day the platoon was reported MIA, the "Gatehouse" was abandoned and St. Teresa and the surrounding area were declared a biological hazard and cordoned off.

The facility and it's secrets were likely destroyed in 2551 when the planet was found and glassed by the Covenant following the Battle of, and subsequent Fall of, Avalon.