This book is concerned with the boundaries of faery. We will investigate the very limits of our understanding- and our definitions- of the faery folk. As we shall see, repeatedly- there are aspects of faery existence that still baffle our attempts to interpret and comprehend them, because they fail to adhere to ideas of a fixed nature and predictable behaviours that are encouraged by strict traditional scientific rationalism. Of course, there are aspects of modern physics which accept mutability and subjectivity, so perhaps faery nature isn't so strange after all. What's more, time and again we shall see the problems of providing permanent labels and classifications. Certain faery types are hard to pin down, and can shift from category to category- sometimes seeming like faeries, but at other times like ghosts, or demons or monsters. This may feel frustrating, but it is part of the wonder of our rich folklore that should be embraced. In this book, we will encounter a range of unfamiliar faeries. We shall discover those that act as witches' familiars and that bring dreams and nightmares; we shall explore the strange forms they can adopt, the surprising ways they move from place to place and- even- the odd games they play. British faerylore will prove to be even more surprising and mysterious than we may ever have supposed.