The Rune of Binding is a word in the Language of Creation that gives the inscriber dominion over the subject, provided it is inscribed properly and empowered with an arcane spell. It is most commonly used by necromancers to ensure the obedience of summoned demons.
The magic to activate a Rune of Binding requires that the caster's strength of will be strong enough to completely overpower the victim's, unless certain conditions are met. If the subject on which the Rune is inscribed agrees to precise terms laid down by the caster, then it constitutes a so-called "Divine Contract," which cannot be broken on pain of death. If the bearer of the Rune tries to break the terms of the contract and/or disobey their master's will, the Rune burns with intense pain, which becomes increasingly debilitating. If the disobedience continues long enough, the bearer of the Rune will die an agonizing death.
In the case of the Divine Contract, the Rune and the terms of the agreement may be inscribed on an inanimate object rather than on the subject himself, but it must be consecrated with the blood of the subject. The subject will still feel agonizing pain if they disobey the terms of the contract, but in general rather than centered on the location of the rune. The object on which the contract is inscribed - usually a piece of parchment or a stone tablet - cannot be destroyed by any known form of physical attack or magic. If the contract ends, the object usually crumbles into dust.
There are ways, however, to free oneself of a Rune of Binding. The first is for the master to release the victim from service, in which case the Rune quickly fades. If the Rune was empowered by the caster's willpower alone, then a sufficient force of will from the subject can overpower the master's, though this is extremely rare and difficult to accomplish. If the Rune was bound by a Divine Contract, then no force of will may be sufficient to break it. Only if the terms of the agreement are met is the victim released from service. In some cases, the terms of the contract may even remain binding after the master is dead. This is why no one should ever agree to a Divine Contract lightly.