Tree Nymphs --
You're walking alone through the woods of Felarya (cause you're an idiot, apparently) when, amazingly, a beautiful, naked girl literally walks OUT OF A TREE! You can hardly believe your eyes, especially when she walks over to you seductively. She leans in toward your face, and you close your eyes in anticipation of a kiss. It's at that point that she begins swallowing you whole before returning back inside the tree to digest you. Congratulations, you just became Tree Nymph food. But, hey, at least you'll make a tasty fruit!
-- Eating Habits
Tree Nymphs have a unique diet. They are completely unable to consume dead flesh (they will immediately vomit it up). Live flesh, however, plays an essential role in their lives, especially with concern to their magic and, surprisingly, their reproduction.
Tree Nymphs have a surprisingly stretchy mouth and digestive system. They are able to consume whole live beings up to twice their size. The Tree Nymph's body doesn't actually digest their meals, that is left to their Tree (See Tree Nymph's Secret).
A Tree Nymph can go their entire lives without consuming eating a single living being (See Magic), or even eating anything at all, instead receiving nutrition directly from their tree, which creates its own food through photosynthesis.
-- Magic
Tree Nymphs are, quite naturally, excellent plant magic users...as long as they are well fed. Tree Nymphs store magic energy gathered from consumption of living beings.
The magical energy of a Tree Nymph is stored inside of their Tree, and is soaked into every fiber of the it. Because of this, Tree Nymph wood is highly sought after by magic-users for construction of staffs and wands.
-- Reproduction
When a Tree Nymph consumes a living being, their tree produces a single fruit. This fruit contains an average of 5 seeds. All seeds produced by a Tree Nymph will grow into a tree, but only 1 in approximately 100 will produce a Tree Nymph when planted.
Because young Tree Nymphs rarely grow close to their parents (thanks to the seeds being distributed by natural causes, such as birds) they have a special memory system. Newborns are born with strong memories from their parents. Some exceptionally strong memories are even passed down from generation to generation.
-- Tree Nymph's Secret
The biggest secret of the Tree Nymphs is this: The body they show is not their true body. Their true body is their Tree...kinda. It is a somewhat difficult concept, but neither the Tree nor the humanoid body is the real Tree Nymph. The easiest way to think of it is that the soul of the Tree Nymph is contained within the Tree, and the body is a sort of remote-controlled interface with others.
The rationale behind keeping such a secret is that the Tree Nymphs do not want to expose what could be considered their greatest weakness. Their body, which is literally created by the tree (and subsequently reabsorbed when the body re-enters the Tree, as well as anything that is contained inside it), is irrelevant when it comes to taking damage. The body can be destroyed without any adverse effect, except for a minor depletion of magical energy needed to generate a new body. However, if the Tree is killed, the Tree Nymph will instantly die.
Comments and questions are always welcome.