Blood Pact

Makes a pact between two intelligent (must understand the pact) entities that is backed by a supporting patron (usually a higher devil or lawful deity).  The two sides freely (cannot be influenced by magic) agree to a pact where each side receives something. The deal must be spelled out in complete detail.  Any vagueness can be interpreted by the DM, usually to the disadvantage of the players.  Once the pact is written, each of the participant's hand is cut, and they simultaneously drip their blood on the pact and a caster enchants the pact (the caster may or may not be part of the pact). Once the pact is enchanted, if either of the two parties fails to meet what was promised in the pact, the patron of the caster may deem (at the DMs discretion) that they are in violation, and send their minions to track down the failing party and drag them back to their domain.  This will not stop until either a new pact is made with the patron, the patron is killed, the failing party is brought to the patron, or, at the DM's discretion, the failing party is killed.