From the back cover:
All About Monstres
This volume contains dozens of new races and individual creatures for use with the Call of Cthulhu roleplaying game. Included here are the following categories: Outer Gods, Elder Gods, Great Old Ones, Great Ones, Avatars, Servitor Races, Independent Races, Fabulous Creatures, and Unique Entities.
These monstrous creations have been collected from over ten years of favorite Call of Cthulhu scenarios; others have been created specifically for this book. The darkly imaginative work of a diverse group of authors is represented here. Where possible each entry begins with a quote describing the monster or entity. Where much about the creature is known, there may be an additional description. If discussing a god, Great One, or Great Old One, notice of any human cult comes next. Further notes discuss habit, habitat, or attack.
An essential aid for players, investigators, and keepers.
"I saw the form waver from sex to sex, dividing itself from itself, and then again reunited. Then I saw the body descend to the beasts whence it ascended, and that which was on the heights go down to the depths, even to the abyss of all being... The principle of life, which makes organism, always remained, while the outward form changed."
-- Arthur Machen, "The Great God Pan"