IOU

The iou is a quest item that appears in the Death Plateau quest. Harold gives it to the player in lieu of payment for a gambling debt he owes from a dice rolling game.

When the player inspects the back of the IOU, they discover that it is really the combination to the equipment room in Burthorpe Castle.

You must have this item in your inventory when speaking with Denulth to complete the quest. If lost, Harold wrote you another one.