The Black Queen Chess Piece is a small black queen carved of stone, about which a coiled stone serpent is wound. It was found folded within a sealed letter addressed to the party by Osman Hamdi Bey, wherein he names it "the key to where she is kept" — a phrase that marks its bearing upon a diviner of great power, whose very existence stands in the way of the consort's full arcane strength. The piece came to light during a search of Osman Hamdi Bey's library, which had been picked over with a discriminating hand; the letter that held it was opened with care, that the seal might be preserved. Its words give one to understand that the Black Queen is bound up in a larger design touching the Padishah's consort and the unlocking of arcane secrets.
Whilst carried by the party, the piece fell to trembling near a great Medusa statue. The serpent uncoiled itself from the queen, slid toward the statue, entered an opening shaped like a keyhole, and set some mechanism working. Thereupon the statue turned outward upon itself, two pillars came down, the waters of the cistern drained away, and a stair was revealed behind the statue where none had been.