Gauntlet is an arcade game by Atari, released way back in 1985, and was later converted to other platforms (such as the ZX Spectrum and Commodore 64). The original coin-op machine was one of the first on which four players could play at the same time. The game was created by Ed Logg and his team. Ed was also the designer of the classic game Asteroids.

In the game, you can choose between four different characters: Thor the Warrior, Questor the Elf, Thyra the Valkyrie and Merlin the Wizard. Each character had their advantages and disadvantages. For example, Thor was very strong, but slow, while Questor was quick but not not so strong, and Merlin had powerful magic.

The object of the game was to collect as much treasure as you could, while killing as many enemies as possible. Each level was a maze-like dungeon, with several exits. The monsters would spawn from the nests, and unless you destroyed the nests, monsters would keep coming at you until your health-meter reaches 0.
Along the way, you can pick up treasures, keys, food, potions and weapons. You'll need the keys to unlock the doors or treasure-chests, and food to keep you from dying. The potions can be used to kill a lot of monsters at once, and the weapons make it easier to kill the monsters in normal combat.

Usually there are more than enough keys to make your way to the exit, so don't worry about that. The exit will lead you to a next level, sometimes skipping several levels. The first few levels are the same every time you play the game, but as the game progresses, the levels will be selected randomly, so no two games will have the same order of levels.

Gauntlet spawned many sequels, including 1986's Gauntlet 2 and later on Gauntlet 3, and many more on other platforms. I recently played a 3D version of Gauntlet on an arcade machine, and although it was fun, it didn't have the same charisma as the original.