Lady of the Small Hexagonal Room in the North Turret
Apparently a past denizen of the castle at Sto Lat. Information is unclear as to who she was or in what capacity she came to occupy a small hexagonal room in the North Turret, but the suspicion, in Mort, is there that she might not have ended up there of her own free will.
To the Bluebeard myth on Roundworld, in which a powerful nobleman either serially murders his wives or imprisons them in remote rooms in his castle, in solitary confinement for life. His last wife, naturally, finds out the horrible truth and turns the tables on him.