The Mechanist's Lair

The Mechanist's lair is a location and possible settlement in the Commonwealth, after the Fallout 4 add-on Automatron is installed.

Background
Hidden deep below the RobCo sales and service center, this expansive bunker was once controlled by the United States Army's Robotics Division as a robobrain research and development center, designated "RB-2851".

However, following the war, the compound beneath Eagle Hill in East Boston became a logical base of operations for the Mechanist.

Settlement information
The Mechanist's Lair is available as a settlement following the completion of Restoring Order. The only buildable area within this huge complex is the medium sized square area in front of the command center. However, this area not ideal for creating a settlement, given that crops cannot be planted, nor can water pumps be installed, meaning any settlers will have to be supported by a supply line. Still, the entire catwalk and lots of machinery that can be scrapped (particularly for steel and aluminum).

There are also several crafting stations in and around the settlement; a robot workbench is set up in the main storage room, while more crafting stations can be found nearby. Another robot workbench is in a room at the end of a hall connecting to the control room, along with an armor workbench, weapons workbench, and power armor station. There is also a cooking stove in Isabel Cruz' living quarters.

Military sublevel
After navigating though the sales and service center, there is a military check-in point with an Advanced lock, down a hall and past a few security vault doors. Past this is a hallway riddled with the laser tripwires; if one does not want to disarm all 40 of them, one can instead go into the nearby room hosting the generator and go through a tunnel into the security office. Toward the end of the office is an elevator with a nearby Master-locked terminal (the terminal does not reactivate the elevator), as well as an Expert-locked security door.

Through the tripwires or the security office, one comes to a small room where the Mechanist addresses the Sole Survivor via eyebot. To the southeast, there is another access port. There is a workshop past this door, and through another door is a military command center. Past a track of train cars that run through the command center is a Protectron holding area, which also has a weapons workbench.

A hallway continues past this to the chief engineer's office; the eastern corner holds a robot workbench, while a staircase in the southern corner ascends to other offices. The offices terminate at an robot assembly floor where, on the northwestern end, a large door will open revealing a tankbot, as well as a room with an armor workbench. A catwalk to the west extends to a workshop area and another access port.

Facilities wing
Beyond this door is another access port, which leads to the facilities wing. Past a small hallway, the Mechanist will address the Sole Survivor again via eyebot before continuing down the hall, past a robot workbench to a flooded floor, next to a power substation. A hallway leads north past a power armor station to a train tunnel; though the door is a flooded and decrepit shipping yard. The yard leads past another power substation up into the management offices, which contains a terminal and weapons workbench.

Research wing
Past the management offices, there is a catwalk and platform which, when activated, will transport one across the facilities level to another access port, and another access port beyond that to the research wing. The wing splits from the main hallway down to the forfeiture room and property storage; the lockup is kept behind a Master-locked door and Master-locked terminal, and holds all manners of supplies. Past the forfeiture room are the robobrain research labs and holding cells.

At the end of the holding cells is a staircase the leads up to the second floor, and a button that opens a secret door to an cargo lift that leads down to the laboratories; past the brain extraction wing and robobrain research and development wing (the former of which contains a chemistry station) is the robot assembly wing to the southeast. In the east corner of this room is a power armor station and a Master-locked terminal (which can be unlocked with the medical terminal password, found on a nearby robot).

Mechanist's lair
Through the nearby door is a robobrain assembly line and another access port which leads to the actual Mechanist's lair, a large room with a workshop, robot workbench and a network of catwalks. The southwest side of the room hosts the Mechanist's control room, while the northeast end of the room has a freight elevator that ascends to a small storeroom, which has an exit back into East Boston.

The control room connects to a hallway which branches into Isabel Cruz' bedroom and living quarters. Further on is a workshop and storage area, with another robot workbench, as well as an armor workbench, weapons workbench, and power armor station. There is also an elevator in the hall that ascends to the security office of the military sublevel.

Notable loot

 * The lead engineer's holotape is found next to the terminal in the chief engineer's office within the Mechanist's lair.
 * The facilities director's holotape is found on a cabinet below the wall mounted terminal in the facilities wing management office.
 * The Mechanist's log can be found in the bedroom adjacent to the Mechanist's control room.
 * There is a fusion core in the generator just past the three doors to enter the Mechanist's lair. A Nuka-Cola Quantum is found in the nearby locker room, on the top shelf of a locker.
 * Another Nuka-Cola Quantum is found in the room after the Protectron holding area; it is on the ground in a small cafe area. One more is in the adjacent chief engineer's office, clutched by what it presumably the chief engineer's skeleton.
 * Two more Nuka-Cola Quantums are found in a box beside a Jangles the Moon Monkey and cymbals monkey near a television, just as one enters the facilities wing.
 * A sentry bot model is on a shelf in the property storage lockup in the research wing. Another can be found near the bed in the bead room adjacent to the Mechanist's control room. There is also a Protectron model on a tray beside a terminal on the second floor of the holding cells.

Appearances
The Mechanist's Lair appears only in the Fallout 4 add-on Automatron.