A Contract-Binder is small and plain beside the Arbiters, about the height of a child, a squat figure in a stiff, square robe of parchment covered in tiny writing. Its hands are broad and heavy, each tipped with a seal of dark red wax that never hardens. Its face is round, smooth, and without expression, and it has no visible mouth. It moves in short, purposeful steps and goes everywhere with a soft rustling of paper. When it seals, it presses both hands to the agreement and the wax glows crimson, and there is a low, chiming note like a struck bowl. It smells of hot wax.

They wait in the courts and halls of the Binding Song, wherever agreements are made, and come at once when one is spoken.

A Contract-Binder seals what is agreed, exactly as it was spoken, and nothing more. It does not judge whether the agreement is fair, and it does not warn. It seals oaths, promises, bargains, and treaties alike, and once it has sealed one it takes no further notice of it.

Its seal makes an agreement unbreakable and enforceable across all planes. A sealed promise becomes a tether between those who made it, and to break it wounds.

Visitors come to the Song to seal contracts that cannot be broken, and the Contract-Binders are the means. Their danger is that they seal carelessly worded promises as faithfully as careful ones.

Travellers say the seal of the Song shows afterwards as a faint red mark on the palm of each party, and some on Caeldon who claim to have made such bargains show the mark. Whether those marks are real, or only scars, is not known.