If you have a central altar about which you cast your circle, you may place in the center of that altar a large crystal so that it becomes a focus for all forces, macro- and micro-cosmic. Over time, this crystal will begin to resonate with the energies you have invoked in your circle. It will serve to house fragments of your rituals and spells, collecting and focusing remnants of magical power long after the spells which spawned that power have dissipated.
This crystal, whether a natural cluster or a sphere, should be fairly large so as to house all of the energy it will absorb. Before being placed on your altar, you should wash the crystal in an infusion of mugwort and sea salt.
Should the crystal fracture or break, care must be taken to collect all of the pieces. These pieces then may either be used for magical work or may be buried in a garden or sacred spot. They may be disposed of by placing them in a deep lake or pond.
After several years of passive charging, the crystal may be used at any time with almost any spell. It may be taken in both hands during the casting of spells to give your work extra power. If you are missing a component for one of your spells and doubt the spell will work, the battery may be used to overcome and compensate for the missing ingredient.
It will take several years of regular ritual and spell work to fully charge the crystal. Once it is charged, you will sense it as will all others who are psi-sensitive.