Sometimes when you collect your Living Wood you will spawn a Disturbed Spirit, just before you finish collecting the wood, who will attack you. Be sure to re-collect the Living Wood after the fight. Living Wood will also drop from all Treants.
Rhetta Stonejaw is atop a large rock shelf.
Find and smash the three Spirit Cairns to find out where the Spirit is hiding.
Find the Stranglewood Spiritroot and examine it to spawn Orlan (who is NOT happy to meet you).