There are three levers that each open a door to the Antechamber.

• East door:
  • Main: behind a door in the Great Hall. The The Great Hall Partitioning Plan reveals the two locations where it could be.
  • Backup: find a Key to the Secret Garden, then use the lever in the Secret Garden (permanent unlock by breaking a wall).
• South door:
  • Main: find a Broken Lever and use it in the Greenhouse.
  • Backup: behind a breakable wall in the Weight Room (permanent unlock).
• West door:
  • Main: find a Key to the Secret Garden, then use the lever in the Secret Garden.
  • Backup: behind a door in the Mechanarium.
• North door:
  • Main: in the Inner Sanctum.
  • Backup: in the Throne Room.

September 8, 2025 9:07 PM (GMT+2) After having figured all of them out already, I found The original gardener’s logbook which actually reveals the location of all main and backup levers (except the north ones).

• Denny’s notes about Antechamber levers