From the back of the box:
In the heart of the City-State of Brairwood, capital of Calandia, lie the confines of Briarwood Castle. Home to the Invincible Overlord, the Castle's interior has always been a mystery to outsiders. Now you can be privy to the closely-guarded secrets of Briarwood Castle in this two volume set, which includes The Briarwood Castle Guidebook and The Dungeon Book, plus a seperate parchment GM's map depecting the dungeon controlled by Ralf, a lich whose quest for power could have a profound impact on the City-State. This set provides exciting material for endless variety of fantasy roe-playing scenarios.
In the adventure you are convicted criminals of the City-State. The Overlord himself has offered to save you from the Death penalty if you can find the vulnerabilities in the Castle's defenses and enter the Castle from the outside of its walls
Someone close to Lucius II is betraying him, and that person dules over the depths of The Old Bathhouse Dungeon and Ralf's Dungeon. These dungeons hold a legacy of evil, and death awaits those who venture here!
The adventure is for 4-6 Player Characters of Skill Levels 20+. Six evil pregenerated Player Characters are provided for this adventure, or Players may generate thier own. The Special Dungeons may be used either with the adventure in this set, or in an existing adventure os campaign.