There are forests, and then there are Forests. Little-f forests are made up of living things. Capital-F Forests are themselves alive. They can think, they can feel. It may seem unlikely that consciousness could arise from an aggregation of trees, moss, grubs, bears, and whatever else, but people have been wondering how a network of neurons could do the same for a long time, without much more in the way of clear answers.
Every Forest has a heart (perhaps coincidentally, perhaps not, so do Hells) which is the core of its being. It's possible to replace one's own heart with a piece of a Forest's heart. Getting to the heart is much harder than the procedure itself. People who do this are called grugach. People who do this are generally some combination of desperate, hateful, and unhinged.
Becoming a grugach hollows you out, physically and spiritually. On the surface you might look and act much as you once did (though roots can be seen creeping through their veins and the shoots poking through their follicles) but beneath you belong to the Forest. Past your shifting moods and passing whims, your tics and aesthetics, at the core of your being, your goals and drives are replaced by the Forest's.
Stats: As Elf, plus:
Taproot Soul: Grugach's lives are no longer sustained by mere animal processes but by the Forest itself. Unless killed by means innately opposed to life and flourishing (necromancy, the undead, curses and cursed weapons, demons, particularly noxious pollutants, and the like) they will be reborn in their Forest's heart in seven days and seven nights.
Grudge: Grugach can hate with a depth unmatched by animals, and an urgency unmatched by plants. If you seriously piss one off then until they're dead the result of rolling a 1 on any random encounter table will be replaced by that grugach pursuing its grudge. They may not attack outright however. Suggestions for how they might act based on reaction roll results are as follows:
2 or less: Murderous. They want you dead right now, and will use hit and run tactics, luring you into traps and ambushes to do it.
3-7: Humiliation. They'll beat you, scar you, steal your stuff, but leave you alive to rue the day you offended them.
8-11: Poisoned Gift. They'll give you misleading advice, cursed treasure, subtly poisoned rations, or the like to make you the architect of your own downfall.
12 or more: Assimilation. They'll attempt to kidnap you or recruit you to have you de-hearted and turned into another grugach.
Any grugach with 8 or more HP is Bough-Crowned, and can step into a plant to emerge from another plant within line-of-sight.
Cooshee (also called Fairy Hounds, Invert Dogs, Hark-Snarks, Noddymauls)
Imagine a world like a sky full of endless clouds drifting by. You might look from one cloud to another, see shapes and movements suggested: a face, a mountain, a head of broccoli. Suggested, but never realized, never settling between moment to moment and view to view. There would be no true or false, no this and not that, only maybes, might'ves, possiblies. This is the world as it was. This world was boundless, this world was free.
Then there was light, and the light was blinding.
Where the light went there followed shadows. When the light blinded there were things that could not be seen. Those it burned were scoured away from the unharmed. Now split from back then and will be. Reality fractured and calcified.
Many of the things called fairies are vestiges of this world-before-light, who took shelter in the mists at the furthest reaches of everything. The names they claim, the forms they take, the roles they play, these are not truly them. Unvarnished truth is corrosive to them, and so these things are like parasols that fairies carry with them as a bulwark.
Cooshee are not, technically speaking, fairies. They are fairy domesticates. Just like fairies wear masks to protect themselves from (non-)existence, they can put masks on other creatures to detach them from the same. Whether they were once man or beast or punished fey, something kept in the kennels of Fairyland will eventually be subsumed by the mask of the mock-dog, become a cooshee, and stalk at the feet of their masters.
AC: As Chain
Atk: Claws & jaws 1d4/1d4/1d8, Overbearing
Move: As horse
Int: As someone pretending to be a dog
Mor: 7, or 10 if their master's around
Overbearing: Any human-sized or smaller target hit by a cooshee's claw attack must save or be knocked prone. A cooshee's bite attack automatically hits any prone targets.
Invisible Web: Once per day a cooshee can howl to make an attempt to move away from it fail. Paths will imperceptibly twist back around on themselves, doors will open into the same room, and suchlike.