The Tower of Indomitable Circumstance (1981)

From the front cover:

"Dare the Black Tower! Brave the Initiation Test of the Old Order! contains Maps of the Land and the Black Tower. This first-time, or solo, adventure can be used with almost any fantasy role playing system!'

 From the web:

The God Math needs you! Only the daring enter the ancient Tower to prove worthy to serve him. Maps of each level and what lies in each are furnished in this 32-page Guidebook, as well as a nasty surprise for unwary players.