Waldgeist

Constant Spells — A constant spell affects the monster without the monster needing to cast it, and its duration is unlimited. If a constant spell gets counteracted, the monster can reactivate it by spending the normal spellcasting actions the spell requires.

Forest Guardian — A waldgeist is compelled to investigate the sound of wood or trees being damaged, such as by being burned or chopped down. A waldgeist that hears such a sound must succeed at a DC 26 Will save or spend all their actions moving toward the sound until they identify the cause. This can't be used to compel a waldgeist to leave their bonded woodland. A waldgeist that succeeds at their saving throw is temporarily immune for 10 minutes.

Void Healing — A creature with void healing draws health from void energy rather than vitality energy. It is damaged by vitality damage and is not healed by vitality healing effects. It does not take void damage, and it is healed by void effects that heal undead.

Woodland Dependent — A waldgeist is mystically bonded to a single forest, jungle, orchard, grove, or other similar large, wooded area and must remain within it. If the waldgeist moves outside their bonded woodland, they're immediately destroyed.

Lignify (incapacitation, primal) — The touch of a waldgeist transforms flesh into wood. A living creature damaged by the waldgeist's lignifying hand Strike must succeed at a DC 24 Fortitude save or become Slowed 1 (or Slowed 2 on a critical failure). Further failed saves against lignify increases the slowed condition. Once a creature's actions are reduced to 0 by lignify, that creature becomes Petrified, except they're transformed into wood instead of stone.

Possess Tree (primal) — Frequency once per 10 minutes

Effect The waldgeist touches a tree to merge with it, possessing it for up to 1 minute. They can end this possession early as a free action at the start of their turn. While the waldgeist possesses a tree, they lose the incorporeal trait, fly Speed, all resistances, their non-constant spells, and their lignifying hand Strike. Additionally, their size increases to Huge, they gain resistance 5 to bludgeoning and piercing damage, weakness 10 to fire, Speed 20 feet, and the following branch Strike.

Melee 1 branch (reach 15 feet) +20, Damage 2d12+9 bludgeoning.

While a waldgeist possesses a tree, any damage that would be dealt to the waldgeist is instead dealt to the tree. The tree has 60 Hit Points. When the tree is reduced to 0 Hit Points, the waldgeist is immediately ejected, and the tree is destroyed.