Gateway to Apshai is an action-RPG where turmoil has struck the land, and only the magic of the Temple of Apshai can bring salvation. The temple's location has been lost in time, and many heroes who sought it have fallen. A legend speaks that the blood of a great hero will be enough to reclaim the temple, but this "greatest hero" is now gone. Fortunately, the wise man Merlis has found the hero's son, whose blood can still fulfill the prophecy. With haste, Merlis leaves the youngster in the dungeon pits to fend for himself.
As the descendant of a hero, the player starts with basic stats and equipment in 4 areas: Strength, Agility, Luck, and Health, as well as a dagger and leather armor. The player must choose a number between 1 and 99 to generate the dungeon. Once begun, the player explores the dungeon, hidden until explored, with four directions to move and standard abilities mapped to different controls. The player can fight, use spells like LOCATE and SEARCH, or pick up items and scrolls found in the dungeon.
The Gateway to Apshai is guarded by various creatures such as snakes, swamp rats, bats, and more. These enemies are only visible when they are in the same room as the player. The game features a timer that teleports the player to the next dungeon after 6 minutes and 30 seconds have passed. Some versions offer the option to manually leave the dungeon at any time. Dungeons get progressively more difficult with faster and more vicious enemies.