From publisher blurb:
TERATOGENICON - our most impressive book so far - is a collection of tables and essays on how to create your own monsters.
It contains one chapter for each of the fourteen most famous monster types (aberrations, beasts, celestials, constructs, and so on). Each chapter examines specific habits, appearance, goals, traits, powers, origins, and many other topics. In addition, the appendixes will help you to create stats (for both old school and contemporary games), to roleplay monsters, and to include all monster types into a coherent whole, among other things.
The book is inspired by the most famous RPG in the world (in its current format and by its earlier "old school" version) but is mostly system-less. Use it as inspiration for ANY RPG of your choice, or even for your own stories, comic books, videogames, etc.