From Halopedia, the Halo wiki
The stronghold was a pre-built structure that was dropped from a Banished vessel in orbit onto the surface of a planet, Halo installation, or other celestial body. Upon impacting the ground, massive spikes on the underside of the structure burrow deep into the terrain and act as a sturdy foundation.
The Tower has a main entrance and a side entrance. The Tower itself was composed of three floors of prisons, accessible via a gravity lift at the base of the structure. The top floor contains a large chamber with two torture devices. There is a security building at the base of the Tower, which can put the facility into lockdown. There is a landing pad at cliffside of the base.
After the UNSC's defeat at Installation 07 circa December 13, 2559, the Banished forces led by War Chief Escharum occupied the installation. The Tower was one of the many Banished outposts deployed across the ring to maintain control. Escharum ordered his troops to hunt down and capture UNSC survivors. The prisoners of war were processed at Redoubt of Sundering, then taken to the Tower for torture and interrogation by its warden Chak 'Lok. Survivors were then brought to the House of Reckoning. Spartan-IV Hudson Griffin was brought to the Tower following his captured by the Banished after a failed assassination on Escharum. Combat Medic Lucas Browning was also taken to the Tower after the Banished forced him to release the Xalanyn known as "The Harbinger" from her cylix.
By May 28, 2560, Spartan Griffin was the only prisoner within the Tower, with only a handful of marines being held at the base of the Tower. Having learned of John-117's survival, Escharum ordered Chak 'Lok to lure the Spartan to the Tower using Griffin's distress signal. John-117 stormed the Tower, fought through the Banished troops defending the outpost, and reached the top floor, where he killed Chak 'Lok. Despite being freed from his torture device, Griffin succumbed to his wounds, but told John-117 of the Banished's search for a Forerunner facility known as the Conservatory. The facility was put out of use following Chak 'Lok's death.
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