Dungeon Full of Monsters is a modular megadungeon for use with Labyrinth Lord and other old school fantasy role-playing games. The megadungeon is composed of 50 individual sections, separated into 5 different levels. You can assemble these in any configuration you like, either randomly or not, either before the campaign or on-the-fly in play. You can also use these sectiosn on their own, without reference to the larger dungeon itself. The second half of the book contains dozens of monsters, illustrated in full colour, often with multiple variations and types. Combined with the unique monsters located in specific dungeon sections, this book contains over 150 different monster stat blocks. There are criminal organizations, insane cultists, meddling deities, evil wizards, undead kings, infernal demons and other invaders from beyond the stars, numerous unspeakable horrors and arcane beasts, and even a few rival adventurers. Use these monsters with this dungeon or any other. Specific conversion guidelines for The Nightmares Underneath are also provided.