While the Zombies mode in Call of Duty: Modern Warfare 3 has a more open world than previous entries, there are still convoluted secrets to be found. There is a locked vault at section H7 on the map that gives only a chessboard next to it as a clue.
How to Find Locked Vault in MW3 Zombies
The locked vault is located in the southeast section of the map in the H7 square. The vault is underneath Shahin Manor, and players will have to descend down a rope in a room to the left of the main entrance. The doors to the vault are locked, and a chessboard suspiciously sitting next to it.
The chessboard is key to unlock the vault, which contains a few large Aether caches and Gold Bars that are worth 3,500 Essence each. However, one of the caches will transform into a Mimic, so be ready to fight.
How to Solve Chessboard Puzzle in MW3 Zombies
There are four pieces on the chessboard, and each represents the location of the transmission device on the Zombies map that needs to be activated to open the vault door. Anyone in the game can activate these four devices, and here are the locations for all four:
The Bishop piece transmission can be found in the tunnel north of Legacy’s Fortress. The boss will be by himself and will drop the device when defeated.
The Knight transmission can be found on a few mercenaries in an armored vehicle traveling the railroad that circles most of the map. Grab a car and follow the railroad until seeing a lone red car on the map. Defeat the Knight to get the device.
The Pawn transmission has no boss to defeat, and is in a shack in the northeastern corner of the map. The device will be inside, but will spawn a Disciple and a horde of enemies.
The Rook transmission is in the Ghalia Seaside Hotel on the west side of the map. The boss will be on the fourth floor surrounded by mines and a sentry gun.
For more Modern Warfare 3 Zombies secrets, check out how to get the Tactical Negotiator Blueprint.