The Gem of Purpose is an essence gem which grants a small bonus to all three ability scores (Body, Mind, and Spirit). It is exclusive to followers of the Way of the Closed Fist, and there is no equivalent for followers of the Way of the Open Palm. It the weakest gem in a series of gems with similar effects, the next being the Gem of Struggle.
In-game description: "The key to getting what one wants is to first know what it is and what it takes to get it. This sense of purpose empowers the truly strong. A clarity of purpose and the willingness to commit everything to see it come to fruition are hallmarks of one who commands fate."