A thousand years prior to the first war, the blithe misuse of magic by the Highborne drew the infamous Legion to Azeroth's doorstep. This was a war of great calamity, and it took the combined effort of every race just to ensure Azeroth's future. The Fey were no exception, being denizens of the Emerald Dream they bravely fought alongside the Kaldorei Resistance and helped secure a doleful victory over Sargeras' army. After the founding of the World Tree Nordrassil, the Fey (Dryads, Faerie Sprites, Pixies and Grell) agreed to help police these sacred territories from further threats.
Imps' relation to Pixies?Edit
Kurgatok calls his imp Keb'ezil a pixy, during an exchange involving the player, in  ω τ ϖ. Due to the context, it is apparent that the term pixy was used satirically, as an insult. The Fey most rumored to have any relation to the imps of the Legion are the Grell, which are suspiciously similar in appearance. This could just be a coincidence that Blizzard decided to use the same skeleton on both races.
Pixies are winged human-like creatures often associated with England and Scotland.