This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Dryad (Greek)
A dryad is a tree nymph or tree spirit in Greek mythology. Drys signifies "oak" in Greek. Dryads were originally considered the nymphs of oak trees specifically, but the term has evolved towards tree nymphs in general,. Often their life force was connected to the tree in which they resided and they were usually found in sacred groves of the gods. They were considered to be very shy creatures except around the goddess Artemis, who was known to be a friend to most nymphs.
Dryads, like all nymphs, were supernaturally long-lived and tied to their homes, but some were a step beyond most nymphs. These were the hamadryads who were an integral part of their trees, such that if the tree died, the hamadryad associated with it also died. For these reasons, dryads and the Greek gods punished any mortal who harmed trees without first propitiating the tree-nymphs.