When the player enters the house, it yields a number of intriguing objects: an ancient brass lantern, an empty trophy case, an intricately engraved sword, etc. Beneath the rug a trap door leads down into a dark cellar. But what initially appears to be a cellar is actually one of several entrances to a vast subterranean land—the Great Underground Empire. The player soon encounters dangerous creatures, including deadly grues, an axe-wielding troll, a giant cyclops and a nimble-fingered thief. This man makes mapping the maze difficult because he removes things you put down in the rooms to navigate by. Yet he has an important use.
The ultimate goal of Zork I is to collect the Twenty Treasures of Zork and install them in the trophy case. Finding the treasures requires solving a variety of puzzles such as the navigation of two brutal mazes and some intricate manipulations at Flood Control Dam #3.
Placing all of the treasures into the trophy case scores the player 350 points and grants the rank of "Master Adventurer."