As the incarnation of the highest ideal of beauty, nymphs are hard to define physically. Few have seen them without going blind or risking death at the prospect. The quality they all share, however, is that they are incredibly, painfully beautiful, alluring and charming in every possible way.
A nymph rarely has cause to enter combat. When forced into a dangerous situation, they can rely on their inherent beauty, blinding all who lay eyes upon them. If the situation becomes even more dangerous, they can disrobe, killing any who see them simply by exposure to such raw, natural lovliness. Nymphs also possess a mastery of druidic magic, and an inherent ability to walk between worlds, teleporting short distances.
Nymphs lead solitary existences, but rarely desire much in the way of interaction, anyway -- they find that others despoil them by their mere presence. Even other fey are usually fairly unwelcome. They largely tend to their places of natural beauty, ensuring that death, decay, and suffering do not overly trouble it. In this role, they do associate with the animals and plants of the wild, and often use these creatures to protect their homes from any unwanted intruders (or innocent victims).
Nymphs despise ugliness in all its forms, whether good or evil, and often seek to eradicate it. A nymph's definition of "ugly" may be fairly extreme, as well: a maiden many find beautiful may disgust a nymph.
In addition to their intimate knowledge of the surrounding area, nymphs reportedly provide serveral more esoteric benefits. It is said that the kiss of a nymph can remove all painful and troubling memories, and that a simple lock of hair from a nymph is enough to knock a person into a deep sleep (if used in a power or a potion), or to increase the Charisma of anyone who bears it. It is also stated that a nymph's glade can impart attractiveness to any who visit it. Finally, tragically, a nymph's tears are important ingredients in love potions.