D: Sigil

Magically seal a bargain between you and [dice] counterparties by scarring your Sigil and awarding temporary control of everybody’s souls to a devil. Free assent is required, but may be compelled by factors external to the magic, such as a dagger to the throat.

Megrims (as in the Geas spell) rewards temporary deviation, and ignoring the covenant completely allows the devil to take permanent possession, which causes death and eternal torment. Removing your Sigil before the end of the agreement is a breach of contract.

Devil + Contract

From Wonder & Wickedness