In Gateway to Apshai the player assumes the role of an unnamed adventurer, who tries to survive a series of increasingly difficult dungeon levels filled with both treasure and monsters.

Level 8 of the dungeon perpetually repeats until the player runs out of lives, ending the game.

The player's character is summoned to the chambers of an old priest called Merlis, who informs him that he is the son of the greatest warrior of Apshai, and that it is written in the prophecy that only he can reclaim the fabled Temple of Apshai and rid the land of its monsters and curses.

As play progresses, they obtain new weapons, armor, potions, eyeglasses, and scrolls containing magical spells.

[3] ANALOG Computing criticized the lack of a save game feature, but praised the replayability and speed of the gameplay, graphics, and loading time.