I am interested too . There is no info on the Net anywhere . Spent 1 hour with a ranger's help on the Yael side and no Stone Caller on track .
I killed him just after the drop down, into the ruins/castle. Have also seen him deeper in. Any elemental can be his PH I believe. Just park in an area with a lot of elementals and clear, and pray.
The wizards that are PHers for other named will be PHers for Stone Caller (all wizards?). I've seen him most often in the first building past the Slab camp (between Slab and Docks).