Signed: First 400 Joe Hill & Israel Skelton
First appearance: Key to the Moon (one-shot, Guide to the Known Keys)
Use: Allows entry to the afterlife
Door: The Moon
The Moon Key allows the user to open the moon, as though the moon itself was a door. You can pass into the door taking you to a “backstage” of the world, passing into the afterlife gently.
This key is forged and used in the side story Locke and Key: Guide to the Known Keys. In the story a generation of the Locke family has a sick child, Ian ,who cannot be healed by the mending cabinet. The child is taken to the moon by balloon as though the world is a stage and passes gently to the next world.
Source: Locke & Key Wikia