[Emelio Lizardo]

If I might make a totally odd suggestion. Since Tree Lords (ents) are notoriously neutral when the spell is cast it should result in a new magic site that is the tree lord. He might decide to ally with you and turn up in a battle, but his real concern is making the forest a safe place for trees. So he add growth and life to the province, pumps vine critters into PD if he likes you, and does attrition attacks on eco unfriendly troops. If you attempt to build a castle in the province he should attack you and make the province independent if he wins. Then he builds for max defense. Give him an enter site option for any nature mage (pluses for druids) that lets you make deals with him.