An action-adventure game developed by Blizzard North and released by Blizzard Entertainment in December, 1996.
Set in the Kingdom of Khanduras, Diablo has the player take control of a lone hero as he or she battles to rid the town of Tristram of the titular Lord of Terror and his demon minions.
Diablo was a best seller and following the first game's popularity an expansion pack, entitled Diablo: Hellfire, was released in 1997. This was followed by a true sequel, Diablo II, released by Blizzard, in 2000.
Diablo first tried to possess King Leoric, the local ruler of Tristram, but due to his weakened state and the strong will of the King, Diablo failed to gain full control. Therefore the demon abandoned the King, which in turn left the King crazed and senseless. Lazarus then kidnaps King Leoric's younger son, Prince Albrecht. He leads him deep into the catacombs where he inserts the demon's Soulstone in the Prince's forehead. This allowed Diablo to possess and warp the prince, thereby attaining material form. Diablo may have a body now, but he is far from his full power, so he bides his time and summons countless hordes of demons, infesting the entire underground complex, gradually turning the region into an outpost of Hell.
The maddened King Leoric accuses the townsfolk of Tristram with the kidnapping of Albrecht, and has several people executed. His loyal knights try to calm him, but as the crazed king has completely lost his sanity they are forced to kill him. His dying words are a terrible curse, damning the knights into unholy servitude. Meanwhile, Lazarus emerged from the catacombs and rallied the townsfolk, leading them deep into the catacombs in order to save the prince. This turns out to be a trap - instead Lazarus leads them to the lair of The Butcher. Many of the townsfolk are slain by the demons. Afterwards Lazarus flees deeper into the underground dungeon.
Demons appear in the countryside as the Lord of Terror regains his strength in the heart of the labyrinth and prepares for the time when he would once again emerge to seek his brothers - Baal andMephisto - and free them as well. It seemed to be a matter of time until the Prime Evils gained dominion over the entire mortal realm.
This is where the player comes in. As he or she fights their way through sixteen levels to face Diablo, they encounter various monsters, quests, tomes, scrolls, weapons, and other miscellaneous items.
At the end of the game, the hero removes the Soulstone from "Diablo's" head. To the players surprise, Diablo begins to melt away revealing Prince Albrecht's body underneath. The hero then pierces his or her head with the Soulstone, attempting to contain the Lord of Terror. However, the end of the game hints at a darker outcome. The final scene depicts the hero, swathed in a shadowy, hooded cloak. The closing words are foreboding:
"The Soulstone burns with Hellfire as an eerie red glow blurs your vision. Fresh blood flows into your eyes, and you begin to hear the tormented whispers of the Damned. You have done what you knew must be done. The essence of Diablo is contained for now.
You pray that you have become strong enough to contain the Demon and keep him at bay. Although you have been fortified by your quest, you can still feel him, clawing his way up from the dark recesses of your soul.
Fighting to retain control, your thoughts turn toward the ancient, mystic lands of the Far East. Perhaps there, beyond the desolate wastes of Aranoch, you will find an answer.