Diablo is an isometric strategy RPG and one of the most well-known examples of the action-RPG subgenre. Although some of the game mechanics resemble a typical RPG, all actions are done in real-time just like in an action game. The player have to kill hordes of monsters through randomized dungeon levels in order to gain experience points, gold and a variety of equipment to bolster the hero's monster-killing potency.

Set in the fictional Kingdom of Khanduras, located in the world of Sanctuary, Diablo has the player take control of a lone hero battling to rid the world of Diablo, the Lord of Terror. Beneath the town of Tristram, the player journeys through sixteen dungeon levels, ultimately entering Hell itself in order to face Diablo.