Dryad

Greek mythic traditions speak of two species of guardian tree spirits: Hamadryads, which are permanently attached to their trees and sometimes die when their tree is cut down, and Dryads, which are free to leave their trees and wander or dance in the groves of the forest.

"Drys" is Greek for Oak; this suggests a strong association with the Oak tree.

Mythical Associations
Dryads are often described as companions to the Moon goddess Artemis, the they sometimes accompany Dionysus, the god of wine.

It is unlucky to see a Dryad, or to remain in their company.