Diablo is an action role-playing video game. The player moves and interacts with the environment primarily by way of a mouse.[12] Other actions, such as casting a spell, are performed in response to keyboard inputs.[12] The player can acquire items, learn spells, defeat enemies, and interact with non-player characters (NPCs) throughout the game.
The dungeon levels are procedurally generated with themes for each level; for instance, the catacombs tend to have long corridors and closed rooms, while the caves are more non-linear. The players are assigned a random number of quests from several tiers; these quests are optional but usually offer powerful unique items as rewards and help to level up the character and/or reveal more of the backstory. The final two quests are mandatory in order to finish the game.