The Tower of Druaga

The player assumes the role of the hero Gilgamesh, whose goal is to rescue the maiden Ki (カイ, Kai) from the demon Druaga. To do this, he must traverse through 60 floors of an immense tower. Gilgamesh comes equipped with a sword, which he can use to defeat monsters, and a shield, which can be used to block magical attacks. The monsters get progressively more difficult as the game progresses, beginning with simple slimes and culminating with Druaga himself. Each floor consists of a maze filled with monsters, and a randomly placed locked door leading to the next level. The player must navigate through the maze to find a randomly placed key that unlocks the door. In addition, each floor contains a hidden treasure, which appears once the player has performed a specific requirement. The player's starting position is also randomly determined; however, the hidden treasure always appears in the same position the player starts from when revealed. The mazes themselves are not random, but there are various predetermined patterns. Some of the treasures are merely helpful items, some are detrimental, and some are essential to completing the game including the Blue Crystal Rod, the game's most important item; without it, Druaga will not appear and the player will be forced to return to an earlier floor.

Source: Wikipedia, "The Tower of Druaga", available under the CC-BY-SA License.