Soul Prisms

Soul Prisms are encountered in Ultima VII Part Two: Serpent Isle.

Description
These items are very much needed for the final capture the Banes of Chaos. They essentially are long-term prisons, since the ether gem in the Black Sword can only hold all three of them for so long and nothing can be done with them during that time.

The process to create them is thus:
 * First, ask Ducio to craft a Worm Gem by giving him the 3 worm hearts. You only need nine to make three of them.
 * After the gem is created, you must cast "Create Soul Prism", which was given by Torrissio. This turns the Worm Gem into an empty soul prism.

Treating The Soul Prisms
Because the Soul Prisms will not be able to hold a powerful spirit for long, they have to be treated appropriately. For instance, in the case of the Banes of Chaos the Avatar had to treat each prism with the fitting water from one of the Shrines of Chaos in order to be effective. Batlin skipped this part, being ignorant of it due to not having done the proper research, thus causing the Banes to break out at the worst possible moment.

Trivia

 * A soul prism that captures the soul of a once-living warrior is called a living gem, which is what grants an automaton 'true life'.
 * The need for worm hearts can hit player unprepared - especially when using the Ring of Reagents - often resulting in a frustrating hunt for Ice Worms.