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.