Summoner Belinda:
First, you must speak with Messenger Naran Ashanuk of the Varka Silenos tribe. They've been hiring mercenaries, and this is a great opportunity to earn their trust!
Soul Guide Udan Mardui, the Chief Shaman of the Varka Silenos, has something they call the Divine Stone of Wisdom. You must get it from them!
If things don't go well with the Varka, you should try the Ketra Orc tribe. They also have one of the stones. Good luck!