Head Summoner Radyss:
At first, go to the Messenger Wahkan of the Ketra Orcs. I heard that they are hiring the foreign mercenaries. If so, it is a good opportunity to gain their trust!
The Divine Stone of Wisdom that we are looking for is possessed by the Soul Guide Asepha, the head shaman of the Ketra Orcs.
Hack... If things are not going well, change the plan and approach the Varka Silenos tribe. I will pray to Eva for help.