Grand Magister Jurek:
You cannot always be successful at absorbing souls -- there will undoubtedly be occasions where matters take a different path.
Furthermore, you will not be able to continuously absorb souls from weak evil creatures. If you keep trying, your soul crystal will refuse it. Once it reaches a certain level, it will want the souls of stronger evil creatures. If you think you have reached that point, it is time to set your sights higher.
If you try to use two soul crystals on a monster, they will conflict with each other, and you will be unable to use them absorb souls anymore.
Receive Soul Crystal.