Hideous Headcanon: The Warden, The Watchman and the Walled Off Door
Sally's Mind Palace into her Past is guarded by two main restrictive doors. One is the Door Behind The Wall. This is the first line of defense against her retrieving her memories. This door is carved from the richest dark imported oak in the likeness of a great and bountiful tree with gnarled roots and entangling branches, with all manner of creatures residing inside it. The Handle is crafted into the likeness of a Sparrow. (Kim possessed a silver pin much alike in the shape of a flying Sparrow).
The first Watchman is the old caretaker, Mr. Harris. He tried to protect Sally and her family when she was younger, and in her unconscious mind, he still attends to that task.
From there it is down the steps to the basement, into the remains of Emerson Blackwood's private studio and at the center of the underground room...is the ash pit, sealed tight by sturdy steel and iron. Above the grating is chisled the runic warning: Be Afraid.
Should any visitors in Sally's unconscious seek to approach this final door and unleash the past, the last stand of protection is the Warden.
Kim. As Sally remembers her.