Masterbrain is a unique robobrain that controls all the other security robots in the Vault-Tec headquarters in the year 2277. It roams the Vault-Tec administration level but is most likely found near a turret control terminal slightly left of the level's center.
The Masterbrain was manufactured for the Vault-Tec Corporation to act as a kill-switch for all other robotic security measures within the headquarters and still remains active 200 years after the Great War. The Masterbrain is identified by the large Vault-Tec logo on its chassis.
If it is defeated and the Lone Wanderer interacts with it, it will say "You have accessed the Masterbrain's internal mechanism. If you destroy its uplink, it will cause all the automated security units in Vault-Tec to shut down." If you choose to do so, this will disable all other robots in the Vault-Tec headquarters building, with the exception of the automated turrets.
Masterbrain is the only known robobrain without a visible brain.
The brain may have been visible before the glass was covered with dirt.
Masterbrain's paint scheme is unique, and none of the other robobrains in the Capital Wasteland have it.
The Masterbrain was mentioned in some secret F12 coding hinting at Fallout 4 before its initial release. It is unknown what this meant as the Masterbrain has no connection to Fallout 4.