Horned Spirit of the Forest

Hiddne away in many deep forests in the world are spirits tied to nature and the belief of life, death, and rebirth. Following the cycles of nature most are tied to specific regions overseeing the gifts, bounties and curses of said cycles. Most are closely tied to the Feywild and can be found in both dimensions skirting between them at will and defending both. These spirits are mercurial in their attitudes to those who dwell within the forests and as long as the balance of life is met, they leave well enough alone. Nearly all have been catagorised as being humanoid in some form or fashion with wildly fantastical elements such as insect wings, multiple bright or dark colours and any number of difference near impossible to catagroise.
A few though, are given to good & evil. Some look upon all life as sacred and will defend it where at all possible. They do not look to kill but to drive off corruption and evil in all it's forms. They take the form of beings with animlal or plant elements showing a healthy countenance & personality.
The same can't be said for the evil Horned Spirit of the Forest. One of a number of entities or spirits that are found thorughout the world these creatures are some of the darkest of Dark Fey, and a few are thought to be touched by Fiends or carrying their blood. 
These are by far the strangest and most dangerous of all their kind. The Horned Spirit is a hunter, killer, and cannibal that was once human or other sentient creature before corruption by the Dark Fey set in. They are guilty of murder of swathes of the plants & animals of the forest they are linked with. Usually only one or two are found in any given forested region, and when they do the damage to attract the Dark Fey, they will make bargains with them while being shown rites to corrupt those who would harm the cycles of life & death further. These pollute the soul of the would-be spirit further leading to acts of barbarism, violence and cannibalism those they pollute. Eventually they are drawn into one of the rare corrupt groves scattered in deep forest where they blend with the plant-life, taking on aspects of it while killing & eating any animal that comes close. Elements of these creatures blends further with them, warping their spiritual & physical presence further.
After a year and a day, the spirit bursts forth after they go through a transformation where their old self dies off. When they come forward they are as much plant as animal and their soul has been touched by a Fiend that is introduced by the Dark Fey as part of the bargain. What Fiend this is depends on the whims of the Dark Fey, but usually tied to corruption, nature, life and death. They are now allowed to wander a specific region of the forest acting as as monstrous punisher of those who both use & misuse the forest. It does not matter which, as long as those who the Dark Fey and their Fiendish allies believe should be punished. May times this is for some type of personal slight or misguided sense of 'justice'.
Whatever the reason, the first thing many victims will see is a skeletal creature resembling a twisted bush or tree moving in their direction. Then a headlong rush while the spirit and it's crown of mutated horns rush forward to devour it's victims body and soul.