From Halopedia, the Halo wiki
Hidden within an asteroid belt, Midnight Facility is situated inside an asteroid and is said to have enough firepower to destroy an entire Covenant fleet. Unlike conventional prisons, the purpose of Midnight Facility is to make high asset prisoners "disappear". Midnight is well guarded and monitored by an artificial intelligence construct. The facility is equipped with numerous detainment cells, referred to as Cubes, capable of releasing sedative gas to knockout irate prisoners. Midnight has its own security force, in which Zed Rhodros was employed.
At some point between November 2552 and January 2553, the UNSC Coral Sea transferred the San'Shyuum Alo Sebukah, former Vice Minister of Abnegation of the Covenant, to the facility, where he was interrogated by agent Oberon 5 in regards to an interaction he had with the AI Cortana during the Fall of High Charity. Known in the facility as Subject DENVER, Sebukah resided in Cell 56 of the facility's Lambda Block, where he remains as of 2558.
In March 2553, Admiral Margaret Parangosky sentenced Doctor Irena Magnusson to this facility after she allowed Jul 'Mdama to escape from ONI Research Facility Trevelyan. In December 2557, after a terrorist attack on Earth, Gek 'Lhar was detained and interrogated at Midnight Facility. Two months later, in February 2558, 'Lhar managed to escape. His escape resulted in several fatalities among Midnight's personnel and a heightened threat condition at the facility. Following his failed attack on the UNSC Infinity in March 2558, Captain Daniel Clayton was captured and sentenced to Midnight. Benjamin Giraud was detained in Midnight after being captured and he is currently in Cube B-349. Some time after his capture, FERO visited him in his Cube. Giraud was glad to see her but soon learned she actually worked for ONI.
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