Magister Alminas:
Then visit the Ketra Orcs to get the missing fragment, the Divine Stone of Wisdom. If you earn the trust of Asefa, guide of dead souls, through Ketra's Messenger Wahkan and prove to her your wisdom, you'll find it.
If you change your mind halfway, you can get it from the best Shaman of Varka Silenos, Soul Guide Udan Mardui through Varka's Messenger Naran Ashanuk., just bring it to me.