Plot
You were born a chosen one, heralded from birth as an instrument of one of twenty three deities. Your destiny is to acquire the Amulet of Yendor for your God and attain immortality.
After recognising your destiny, you have set off to the entrance of the Mazes of Menace. The amulet is thought to be somewhere beneath the Valley of the Dead.
Thankfully, very few actions are mandatory, many features are randomized, and there are many ways to achieve almost anything. This adds to the strategic challenge and makes the game interesting to replay. As a side effect, there is almost no "story" in the sense of most other games.