If you want to save the tree spirit because you all about that green life, you’ll need a woman’s remains, a raven’s feather, and a black wild horse.
It may sound like a lot but the raven’s feather, you got that from the harpy’s nest where johnny ‘voice was. Both the woman’s remains and the horse is easy to find. Just leave the cave and follow your marker to find the woman’s remains. Then follow the marker again to an open field where you will encounter a pack of wild horses. Slowly approach them and use the Axii sign to tame one. Now hop on it and ride that poor unsuspecting horse back to free the tree spirit.
If you do this AFTER starting the main quest “Ladies of the Wood”, the tree will free the children at Crookback Bog, which will upset the hags and I hate say it but Gran you in danger gurl.
If you do this BEFORE starting “Ladies of the Wood”, the tree will renege on the promise of saving the children. But the tree spirit will be freed and Gran WON’T be in danger. Regardless tho the village of Downwarren is going to be done for.
Note: If this quest is done AFTER starting “Ladies of the Wood” it will have a negative impact when it comes to finding Anna, the Bloody Baron’s wife. If the quest is done BEFORE “Ladies of the Wood” Anna won’t be in the same kind of danger.