Rather than merely command a spirit to depart, you may condemn it and
confine it by a similar means. The process is the same as the spell
Banishment except in that the box is set outright into the flame, and a
condemnation is made wherein the spirit is forced to remain in the vessel
containing the coals. You must then pour a vessel of pure water on the
burning box, extinguishing the flame. As you do this, so that the smoke
does not escape, place a lid on the vessel and seal it with a magical word
of confinement, the lid bearing a magical sign to the same effect.