Once invoked, the runestone creates a key which can later break its connection to its binding stones. The runestone's key must revoke the energies at each binding stone. Most rituals use one or two binding stones; more powerful entities require three. Legends speak of rare creatures that need four.
Note: One can avoid the bound entity's death by invoking the Rite of Proxy. For this, use the runestone on a willing sacrifice. That person's life will be forfeit, and the bound entity is freed. The key thus created will be energized with the soul of the proxy sacrifice.