Askafroa

Ethereal: Askafroas are physical manifestations of spirits within the physical realm. As a result, the Askafroa can only interact with the physical realm magically.

Spellcasting: The Askafroa is a third level spellcaster. Its spellcasting ability is wisdom (spell save DC 16, +5 to hit with spell attacks). The Askafroa has following Druid spells prepared:

Cantrips (at will): Resistance, Mold Earth, Druidcraft
1st level (4 slots): Cure Wounds, Absorb Elements

2nd level (3 slots): Barkskin, Earthbind, Healing Spirit, Spike Growth, Summon Beastial Spirit

3rd level (2 slots): Erupting Earth, Plant Growth, Protection From Energy, Conjure Animals, Summon Fey Spirit, Plant Growth

Shift Form: The Askafroa's default form is that of a green levitating apparition. The Askafroa cannot interact within the physical realm in this form. Using a bonus action, it can shift to a form resembling a humanoid made of bark.

Bark Claw: The Askafroa manifests a sharp bark-covered limb to attack with. Melee Weapon Attack: +5 to hit, reach 10 ft., 1 target. Hit: (1d8 + 3) piercing damage. 

Bark Shard The Askafroa grows a sharp dagger-like piece of bark out of an area of poisonous moss on its body to then throw. Ranged Weapon Attack: +3 to hit, range 30/60 ft., 1 target. Hit: (1d4 + 3) piercing damage. If hit, the target must make a DC 16 constitution save, else take 1d4 + 3 poison damage.

Guardian of the Ash Tree: Whenever an attack is made toward the Askafroa's Ash Tree while it is alive, the Askafroa can teleport and intercept the attack. If the attack roll fails to hit the Askafroa's AC, the Askafroa can take any action or reaction as a reaction.

Vengeful Death: If the Askafroa's Ash Tree is destroyed while the Askafroa is still alive, it'll use its remaining life force and that lingering around the tree to curse all wrongdoers to begin to rot. If the curse is not lifted after a week, all will rot from one's body until only a head remains. If this head is buried, it will grow into a new Ash Tree, and the soul of the wrongdoer will become an Askafroa.