Dryad

Dryads are a kind of fey, found both in the Alfheim  and Midgard .
They are spirits who take the form of beautiful women composed of wood and plants.  While the most common kind of Dryad is bound to an old, hard-wood tree like an Oak or a Walnut, there are a myriad kind of Dryad's, from those who occupy decaying, moss-covered swamp tree's, to those connected to gnarled solitary pines high up in the mountains. 
They are more common in forests with powerful protective forces, be they Elves , or the Circle of Trees. 
They are not necesarily inherently hostile to humans or similar peoples, but they do not view the cutting down of tree's or other acts that despoil nature lightly.