Greenbound creature

A greenbound creature was a type of creature imbued with the powers of the forest and changed into a plant creature. This was the product of a corrupting magical effect known as "greenbinding" that could affect any animal, fey, humanoid, giant, monstrous humanoid, or vermin.

Description
After transformation, a greenbound creature's flesh and muscle were replaced with pulpy wood and thick-corded creepers, and its hair, fur, or features were replaced with a combination of flowers, leaves, moss, and vines. Meanwhile, little branches protruded from the arms, legs, and torso. Otherwise, the creature retained its basic form, though the changes were obvious. Its voice turned deep and gravelly.

A greenbound troll, for example, still looked like a troll, but its arms resembled knobby, knotted tree branches; it had three roots in place of toes; and the whole body was covered in thorns and leafy twigs.

Abilities
A greenbound creature retained its original shape and size and all its powers, skills, and traits. However, it became a plant in all respects and gained a variety of new abilities and enhancements. For one, the greenbound creature gained great strength and better agility. It was more robust, also becoming very resistant to cold and electricity and gaining rapid regrowth of damage whilst still active.

Via tremors in the ground, a greenbound creature could instantly sense the position of anything within 60 feet (18 meters). In forests, the greenbound creature's woody body and leafy exterior provided it with excellent camouflage.

Finally, a greenbound creature gained high charisma and could use this to use several innate spells: entangle, pass without trace, and speak with plants at will, and wall of thorns once a day.

Combat
A greenbound creature fought just as it did normally, but could just slam its foes through brute force. Moreover, the hook-like thorns on its hands and feet helped it grip a creature. It also acquired an almost-impenetrable natural armor with a high resistance to damage that could only be overcoming a magical, bladed weapon.

Greenbound trolls typically used their innate spells to tangle an area with plants and vines, before hurling themselves into a fight to the death as normal trolls did.

History
The elves of the realm of Eaerlann in the High Forest once practiced a technique of divine summoning magic that incorporated greenbinding. Although long forgotten by the 1370s DR, a few who studied ancient lore might well learn it as a form of metamagic. At the caster's choice, with an enhanced summon nature's ally spell, an animal that answered their call could be transformed into a greenbound creature for the spell's duration.

In the ruins of Telardon, a city of the neighboring elven realm of Siluvanede destroyed by the Eaerlanni in the Seven Citadels' War (c. −4500 to c. −4300 DR), hundreds of arcane magic items were left behind and buried in the ground. With centuries of neglect, their powerful magic decayed and their energies mingled, creating a corrupting greenbinding force. Creatures that unwittingly wandered into the area were turned into greenbound creatures. By 1374 DR, the ruins were the lair of dozens of greenbound trolls that had been transformed there.