The Fae or Fey are creatures of chaos, that seem to be mostly composed of magical energy which gives them a constantly shifting form they can change at will. If legends are true they have existed at least since mankind first learned of fire. They seem to have developed a strangely parasitic existence with humanity, who they sometimes prey on and other times play with. The Fae form two courts: Seelie and Unseelie. Also known as Summer and Winter Courts, which are built on a feudal system with the Sidhe as the aristocratic elite. Summer Fae tend to be more subtle and emotionally sympathetic. The Winter Fae tend to be cold, ruthless, and lack the concept of remorse.
A common trait is a weakness to iron, which acts like an allergy or poison to most Fae. They also cannot specifically lie, but take great delight in twisting the truth to suit their desires. So for instance if asked if they know where a kidnapped child is, they may say that you should go into the den of a monster which happens to be related to the kidnapper instead. Even the Seelie Sidhe tend to be known as tricksters with classic characters like Puck being very real.
One exception to the general rules is the Wild Hunt, which can best be thought of as a rogue element of Fae which adhere neither to the summer or winter courts. This is lead by the Erkling, who rivals the raw power of the rulers of the Fae courts. The Wild hunt is full of predatory Fae of various types, though the sidhe are still the most imposing of them on their gigantic black stallions.