Artifact Key

The artifact key is a unique end game item that was added in update v1.0 to The Forest.

Gameplay
The artifact key allows access to the Artifact Ball after the game has been completed on its alternate ending. It is accessed by using the gold keycard to open the door on the yacht. Once the artifact key has been acquired, go back to Artifact Cave. It is used to open the door that conceals the Artifact Ball. When the player is using a Plastic Torch while the artifact key is in hand the flashlight will always be pointed at the key.

Location
Yacht - Requires the game to be completed first. Works only with the alternative ending, where you shut down the Obelisk instead of crashing the plane.

Theory
It is believed that Dr. Matthew Cross placed the artifact key there, as he can be seen on the yacht from a distance. Drawings made by his daughter Megan Cross can also be found outside and inside the locked room.