The Mechanist's lair is hidden underneath the RobCo Sales & Service Center, which primarily sold and maintained terminals. Employees of the service center were specifically instructed not to interact with any abnormal shipments, or else they would be taken for "extensive questioning by our friends downstairs." In the service center's basement, a large hidden door that requires a robot equipped with an M-SAT to open leads into a large underground pre-War facility that was used for the development and construction of Robobrains. The facility was operated jointly with General Atomics and the U.S. Army Robotics Division. Part of the facility functioned as a pseudo-prison, housing prisoners who were later operated upon to remove their brains. After being wiped of memories and subjected to assorted tests, the brains were housed in Robobrain heads and mounted on any of a number of devices, including the bodies of normal Robobrains.
At some point before the events of Automatron, Isabel Cruz discovered the facility while scavenging, and took it upon herself to use it to create an army of robots to save the Commonwealth from anything which may threaten humans.
At the end of Restoring Order, direct access to the lair becomes available via a freight elevator inside a garage northwest of the East Boston Preparatory School. Upon completing the quest, the lair also becomes a new settlement.
- Despite being another interior settlement, this settlement has significantly more customization options than Home Plate, but unlike Home Plate, has a settlement building limit.
- The Mechanist's lair functions like an exterior settlement, in that settlers can be moved here, and supply lines can be established.
- The following settlement crafting options are unavailable:
- There are two small patches of dirt where water pumps can be placed on the top level in the northernmost corner, just outside the entrance to the facilities wing.
- The crafting stations found throughout the complex outside the construction area are linked to your workshop as if they are part of the settlement.
- Several robot parts models are scattered throughout the interior:
- Eyebot model - Near the entrance, on top of some file cabinets in the small Advanced-locked room with a skeleton hanging out the window.
- Mr. Handy model - In the quality control area, on the desk next to the chief engineer's terminal.
- Robot parts model A - Just after power substation A, in a locker.
- Mr. Gutsy model - In the research wing, behind the watch station terminal desk near the entrance.
- Robot parts model B - In the research wing, on a shelf in the property storage room behind a Master-locked terminal.
- Protectron model - In the research wing, on a surgical tray near the medical observation terminal in the observation area above the cells.
- Robot parts model C - In the research wing, near the cerebral reconditioning terminal in the brain extraction area.
- Five Nuka-Cola Quantums:
- One is near the entrance, in a locker just past the initial security doors.
- One is just outside the quality control area, on the ground near an Eat-o-tronic.
- One is in the quality control area, on the ground near the chief engineer's terminal.
- Two are in the facilities wing, in a crate on the ledge to the left by the descending ramp near the entrance, near a Jangles the Moon Monkey and a clapping cymbal monkey playing the video game "Pong" on a console.
- Two Vault-Tec lunchboxes - One is in the production wing at the end of the robot storage area by a skeleton underneath a yellow eye protection poster. Another is in power substation B on a red stepladder behind the generators.
- Fusion core - Near the entrance, in the generator to the left just before the decontamination/laser tripwire corridor.
- Lead engineer's holotape - In the quality control area, on the desk next to the chief engineer's terminal.
- Day Tripper - In the quality control area, near a desk with a skeleton on the upper level.
- Perfectly preserved pie - In the assembly line room, in an Eat-o-tronic.
- Facilities director's holotape - In the facilities wing, next to a Novice-locked ammo box by the facilities management terminal.
- Forfeiture terminal password - In the research wing, behind the watch station terminal desk near the entrance. Unlocks the Master-locked property storage lockup terminal.
- Stealth Boy - In the research wing, on a wooden box to the right of a hole in the floor at the end of the cell observation area.
- Chief scientist's holotape - In the research wing, near the cerebral reconditioning terminal in the brain extraction area.
- Medical terminal password - In the research wing, on a Quantum Robobrain near the incinerator in the robobrain assembly area. Unlocks the Master-locked robobrain production terminal.
- RB-2851 master control password - Given by the Mechanist during Restoring Order, or taken from her body. Unlocks the key-locked master control terminal.
- Mechanist's armor and matching helmet - Obtained at the end of Restoring Order.
- Protectron's Gaze - Carried by the Mechanist.
- Fusion core - In the main room, on a small set of metal shelves under a ramp near a couple of radioactive barrels to the east.
- Burnt technical manual - In the hallway outside the Mechanist's bedroom, on the small set of metal shelves. Only three others exist, and are found on Automatron NPCs.
- Overdue book - In the hallway outside the Mechanist's bedroom, on the small set of metal shelves.
- Mini nuke - In the room at the end of the hallway outside the Mechanist's bedroom, on the shelf.
- Spotlight schematics - In the room at the end of the hallway outside the Mechanist's bedroom, on the large "Hubris" terminal console.
- Eyebot pod schematics - In the Mechanist's bedroom, on the table near the entrance.
- Mechanist's log - In the Mechanist's bedroom, on the table next to the bed.
- Drawing of the Mechanist - In the Mechanist's bedroom, on the table next to the bed.
- Sentry bot model - In the Mechanist's bedroom, on the table next to the bed.
- The player character can confront the Mechanist directly by loading the lead engineer's, facilities director's, and chief scientist's holotapes into the Master-locked elevator access terminal in the security office next to the decontamination/laser tripwire corridor near the entrance, lifting the security lockdown and enabling use of the nearby elevator. Alternatively, the player character can listen to the holotapes from the Pip-Boy when near the terminal. Upon closing the Pip-Boy while each holotape is playing, an automated voice will acknowledge the speaker's voice. Once all three holotapes are played, the automated voice will indicate that the player character must confirm the manual security override by using the elevator access terminal.
- Each time the game is loaded in the lair, the assembly line room spawns robots on the spot, each with a chance of being a legendary robot. However, only a limited number of robots from each line can be destroyed before they stop production.
- Outside the Mechanist's bedroom is a small button on a coffee machine that opens a hidden door at the end of the hallway. The room contains an observation terminal, a missile launcher, two missiles, an unlocked safe, and two packets of Mentats in a drawer.
- This is one of the few interior locations which can be fast traveled to and from.
- The exterior door cannot be opened until Restoring Order is active.
- The entrance door to the lair opens in a similar pattern to that used by the original Mechanist in his lair at the robot repair center in Fallout 3.
- After completing Restoring Order, leaving the building may cause the game to crash. Fast traveling directly to another location, rather than leaving through one of the doors, may solve the issue.[verified]
- There is a chance that the Mechanist's lair cell may become graphically glitched when facing certain directions. Textures may pop in and disappear as you angle the camera, and FPS may drop dramatically when looking in the glitched direction. There is no known fix for this issue so far. [verified]
- The locations of the player character and the player character's power armor may be marked incorrectly on the map when inside the Mechanist's lair. This is corrected upon leaving the building. [verified]