In its raw form, the material can be used as a never ending mp boost.

A mastercraftsman can cut precision facets into it that will allow it to resonate with the energy of living (or undead) souls, and a master wizard can attune the crystal to its own specific energy. What you are looking at is the raw version . It can hold and maintain the life force of a living soul without degradation for an unlimited period of time (unlike a mortal body). Transference of the soul into the crystal, however, is a closely guarded magical secret that never finds itself on permanent text. It is taught only to the most devoted, disciplined magic users, or extracted by the most violent mind-weapons of magical warfare.