The Warlock of Firetop Mountain (1984)

(User summary)

Based on the Fighting Fantasy book of the same title, the game places the player in a vast (multi-screen) labyrinth beneath Firetop Mountain. The labyrinth is randomly generated each time the game is played, along with the placement of its inhabitants: deadly orcs, spiders and slime moulds that patrol the tunnels and rooms. Wielding a sword and bow, the player must find and collect 15 keys and then find the Warlock's treasure chest (drawing the invincible Warlock away to gain access to it) in order to escape with the treasure therein.

The game is only very loosly based on the storyline of the original choose-your-own-adventure book, and bears a far closer resemblance to Crystal Computing's earlier "Halls of the Things" title (both using a similar underlying engine).