"A white porcelain mask with smoked glass lenses.
It is rather unsettling to look at."
The Ghost Mask is an item found in Prisoners of the Elder One. It is located in the Doll Room, searching through the drawer twice (a single search will only yield the Library Key), and is used in several ways: making the ghost in the Kitchen Basement visible, uncovering the right path leading to the Elder One's Hideout, and revealing the entrance to the Necromancer's Room (though it can be entered without it).