The Illhiedrin Book is an adventure for fantasy role-playing games published by Judges Guild in 1981.

The adventurers travel the countryside, finding clues, discovering a mysterious crypt, and dealing with the patrols of invading orcs along the way.

Judges Guild was able to keep their Advanced Dungeons & Dragons license for another year, allowing them to publish adventures like The Illhiedrin Book (1981), Zienteck (1981), Trial by Fire (1981), and Portals of Twilight (1981) before ending that line.

I can't explain why Lieutenant Sladentail is pictured as a griffon when he's human, and I suspect Alcastra is naked on the cover to spark sales.

Worst of all, the characters are never really fleshed out – the DM will know how to run them, but he may never figure out why they are in this adventure in the first place.