The Craftsman's key is an item that can be created with five Null Shards. It is designed by The Craftsman to trap a person and use their soul as a power source. It makes its first appearance in The Room Three. In the game, the player must collect five Null Shards and take them to the font. When all five Null Shards are collected, the Craftsman's Key is created. The player can then use it to cast the projection of Metatron's Cube that opens the portal to the Imprisoned ending.

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