The name of this task is The Devil's Checkmate, with the code being 7453.

There are 4 blackboards which can be found in the classrooms of Disturb the Neighbourhood and Get Out the Vote. The checkmate moves on these boards determines the solution for the code. The full derivations can be found further down.
This code can be input in the map Disturb the Neighbourhood, in the kitchen.

There are 2 blackboards which can be found in the school, at the final area of the map.
On this board in the lit room, the White Queen moves from G3 to C7 to checkmate. Hence, representing 7.


On this board in the dark room, the White Knight moves from F3 to D4 to checkmate. Hence, representing 4.
According to the keypad, White moving symbolises the first 2 digits of the code, making them 74.

In Get Out the Vote, the blackboards can be found in the school in the starting area of the map.
On this board in the lit room, the Blue Bishop moves from G4 to F5 to checkmate. Hence, representing 5.


On this board in the dark room, the Blue Queen moves from H4 to H3 to checkmate. Hence, representing 3.

As Blue is moving, according to the keypad, this symbolises the last 2 digits of the code, 53.
Thus making the final code 7453.

The solution for this Easter egg is 7453, and it can be input in the kitchen of Disturb the Neighbourhood.


Inputting the code reveals this room.


The task displays as having no true reward in the tasks. However, this is inaccurate.


Completion of this task changes the appearance of the chessboard in your sleep room.
Before completion of the task:


After completion of the task:

Let me know if I need to add or change anything.
Special shoutout for Coyle's Therapist for going through the maps with me and helping to figure this out!
Thank you for reading and please give a rating/ award or comment if this guide has helped you!^^