The Embedded is a character in Dark Souls II.
The Embedded was once a human who was tempted greatly by flesh, and knowing that he could not resist it, bound himself with chains and a lock. Before doing so, he created the Key to the Embedded. He then waited for someone to find his key and bring him to his end.
The Embedded is found chained to a door at the top level of Drangleic Castle. After obtaining his key from the Demon of Song, he can be freed by interacting with him with the key equipped. The key is plunged into his face and kills him, unlocking the door behind him.