D1-2: Descent into the Depths of the Earth (1981)

From the web:

This module (titled Descent INTO the Depths of the Earth on the cover) is the 1981 edition and contains the material previously published separately as D1: Descent into the Depths of the Earth and D2: Shrine of the Kuo-Toa. This carries the adventure on from the outcome of the Against the Giants series of modules as the players explore the role of the Drow in instigating the Giant alliances.