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InBlue Prince, there’s a strange black door just outside the driveway that is installed on the side of a giant piece of rock. There’s no obvious way to open it from the outside, but we know how to get it open.
Blue Prince: How to Light the Four Lookout Torches
How to turn on all the white torches with blue flames outside of the mansion.
This door is the entrance to the Blackbridge Grotto, a permanent upgrade that will enhance the capabilities of the terminals around Mt. Holly. To open the door, you’ll need to send some extra power to the Laboratory in the house.
Power Up the Boiler Room
First, you’ll need to draft the Boiler Room with as many doors available to be drafted from as possible (this means two doors leading to blank drafting plots). The Boiler Room serves as a source of excessive power, and can increase the abilities of certain rooms when properly connected to them. To turn on the boiler room’s power source, you’ll need to redirect the lines from the three steam generators in the room to lead into the center console.
First, head down the stairs to the lower level, and halt the rotating treadmill of metal that blocks the red valve on the caged steam generator (turn the red three-sided pipe). Turn the valve on the generator to the on position, and then redirect the line to power up the elevator in the corner by flipping the small blue lever on the perpendicular pipe connection, and the straight red pipe next to the elevator.
Head up the elevator and across the pathway, flipping the lever on the wall on the other side of the barricaded door. Return down the elevator, and turn the straight red pipe to funnel steam from the uncaged steam generator on the ground.
Rotate the three-sided red pipe to the position above, so that it connects the uncaged generator, the line to the center boiler, and the bridge mechanism.Turn on the uncaged generator, then return to theperpendicular blue leverand turn it so it points upwards from the caged generator,
Finally, head back up the stairs and turn on theupper steam generator, and turn theblue lever on the sideto face the boiler. this will allow you to control the Boiler Room console, and point the energy through one of the three doors.
Connect the Laboratory to Power
The next part is going to take some luck, so we recommend drafting aStudyor finding someivory dicebefore trying this so you can make multiple attempts.
TheLaboratoryhas to either bedirectly connectedto the Boiler Room, or it has to be connected to the Boiler Room viaanother room that can transfer powerinside of it. Here are the rooms you can draft between the Boiler Room and Laboratory that will keep the connection intact:
You’ll know that the connection is working when you have activated the Boiler Room console and see the ducts above your headglow with bright blue energy, leading all the way to the box of levers in the corner of the laboratory.
Solve the Lever Puzzle
Now that the lever box is powered on, you’ll need to find out which levers to pull in what order. Look to the right of the box on the wall above the table to see a Periodic Table full of blank spaces and numbers. When you place the elemental symbols occupied by each number in numerical order, it spells out a message (there’s a full Periodic Table on another wall inside the room).
The message spells outPUSHTHREEAFTERNINE, or “Push three after nine.”
Flip Lever #3, then Lever #9, and a cutscene will play, unlocking the Blackbridge Grotto outside and completing the puzzle.
