From publisher blurb:
Stonehell Dungeon: Into the Heart of Hell is the long-awaited sequel to Stonehell Dungeon: Down Night-Haunted Halls. This book contains the final levels of the megadungeon, revealing its most terrifying secrets. It contains almost 600 dungeon rooms for the players to explore, more than 70 unique monsters to challenge them, and 13 new magical items to mystify them.
Stonehell Dungeon is a classic-style megadungeon intended for use with the Labyrinth Lord™ role-playing game, but adaptable to early versions of the original fantasy role-playing game and its retro-clones. It gives the game master the necessary information to run the dungeon, while offering enormous opportunities to customize the site.