The Angel Halo was a psycommu fortress, basically a giant circular structure with a control ship in the middle. It appeared in the Mobile Suit Victory Gundam series.
While the other psycommu systems merely read brainwaves and translated them into machine code to control the weapons, the Angel Halo harnessed the power of hundreds of "psychics," the exact nature of which is unknown (all controlled by one single newtype in the middle) and used them to "devolve" the human mind. It would literally force an adult mind to think like a baby and even further back. It was used to attempt to mind wipe all inhabitants of Earth.
Angel Halo had no outer defenses, it was only guarded by a Zanscare fleet. However, the effect of the structure's systems prevented potential attackers from getting close.
After being destroyed, it fell onto Earth, creating a large impact zone. Seventy years later, during the events of G-Saviour, CONSENT is using the impact site to hide a secret mobile weapon factory under Project Raven, to be used against civilians.