Fey

Fey are creatures from the Feywild, a parallel plane to the mortal realm. The Feywild is also called the Plane of Faerie, Faerie, Faerieland, and many other names. Many are typified as having supernatural abilities and a connection to nature or to some other force or place. The language of the fey is called Sylvan.
There were many different species (or ethnicities) of fey, and connections between them could be hard to identify, other than being natives of the Feywild. A few common threads could be drawn between certain smaller groups, however, while some were simply impossible to classify.
Some fey were strongly bound or associated with specific natural locations such as water bodies, landmarks, or other geographical features. These included dryads, hamadryads, nymphs, naiads, nereids, oreads, and fossergrim.
Other fey were reported as being born from emotions felt while in the Feywild, manifested due to that plane's strange energy. Redcaps, meenlocks, boggles, and mites were all included in this group.
Another group that was easily identified were the hags: annises, bheur hags, sea hags, green hags, shrieking hags, and bog hags were all considered. Night hags, although related, were actually fiends.
One group of fey was confusingly called sprites, despite this being a specific name for one of its included members. All "sprites" were small, mostly humanoid fey, that typically displayed some insect-like attributes (such as wings). Besides the classical sprite for which the group was named, there were the sea sprites, shrub sprites, grigs, nixies, pixies, and atomies. The winterling, despite also being small and winged, was not included.
Yet another diverse group of minuscule fey were the gremlins, who descended from goblins transformed by fomorian rituals. They included the fremlin, galltrit, jermlaine, and snyad. Mites were also considered by some to be members of this group.
Of course, many fey could not be classified into any larger group beyond being related to either nature or emotion.
They were easily adaptable and magical creatures, making so many subvariants that it is impossible to classify them all.