When equipped, this item becomes a spirit emerald (a). While worn, whenever the player creates a familiar pouch they have a 20% chance of not using a charm to create it; a charge is used each time it does not consume a charm. Spirit emeralds have 20 charges and the item is destroyed once they are all used. Using another spirit emerald on it will consume the inactive one and add its charges to the active one. You can combine up to 1,000 charges in an active spirit emerald.
Inspecting an active spirit emerald with full charges provides the option to convert it back into an inactive one, so that the player may use it to forge three of them into a Spirit ruby. The net number of charges is 30 fewer, but the chance to not consume a charm is 30% instead of 20%.