The Hole in the Oak

From the publishers blurb: A hole in an old oak tree leads characters down to a maze of twisting, root-riddled passageways, the chambers of an ancient wizard-complex, and the banks of an underground river where once a reptile cult built their temples. A classic expedition into the Mythic Underworld. Suitable for characters of 1st to 2nd level. 60 keyed areas, rumour table, dungeon background info, suggestions for expanding the dungeon. Keyed in a quick-reference, bullet point format. Statted for Old-School Essentials (B/X), usable with any vintage adventure game. Illustrated by the hyperdimensional James V. West. Cartography by the mycotic Karl Stjernberg.