Caylum's Unbreakable Knott

You touch a length of rope, chain or similar and it will tie a knot around an object or become binding around a creatures hands and feet no larger than huge size. You and the creatures you designate when you cast this spell can untie the knot normally. You can also set a password that, when spoken within 5 feet of the object, suppresses this spell for 1 minute. Otherwise, it is impassable until it is broken or the spell is dispelled or suppressed. Casting knock on the object suppresses Unbreakable knot for 10 minutes and will allow the binding to be removed. The spell when cast will only bind the object or the person it was original cast on until the the rope or chain is broken.

While affected by this spell, the object or person bound by the knot is difficult to break or remove; the DC to break it requires a DC of 18 vrs strength.