From Introduction:
In 1983, TSR released a manual full of creatures in what it dubbed “the third in the series of . . . role-playing aids.” Inside were a collection of monsters that had previously appeared in various modules as well as several that supported the planar cosmology of Gary Gygax. This book poses the question, what if this collection of creatures was not the third, but the first? How different would FRPGs be and the worlds that they implied?
The result is familiar because we still have elves, dwarves and dragons, but these are not the elves, dwarves and dragons we have all become so familiar with. This is due to a number of themes suggested within the pages of TSR’s third installment of beasts which this book tries to present in a playable form.
There are three different broad categories of monsters: Elementals, Fey and Lost World. Within these broad categories is the theme of corruption. Gone is the normal demihuman/
humanoid dichotomy. In its place is a world where the pursuit of arcane power has corrupted large swathes of the world resulting in dark fey, warped creatures of nature and beings trapped in unnatural forms.