From the Back of the Book:
The fey - also known as faerie, or fair folk - are some of the most misunderstood creatures in fantasy games. Some view them as harmless sprites living in the depths of sylvan woods; others see them as vindictive creatures with limitless power who steal children and play cruel and even lethal pranks on those that cross their path. The truth, as might be expected of such an enigmatic race, is that both perspectives are sometimes accurate, although there is far more to the fey than either view would suggest.
For those looking deeper into the mysteries coiled around the fey, another area of speculation is the magic they wield. In some cases it seems quite innocuous, while in other circumstances it is nearly unstoppable in its destructive force. The fey are understandably quite protective of their gifts and the source of these powers. All that most mortals have been able to learn is its name: the Reverie.