Diablo I logo
Diablo II logo
Another game universe, this one totally RPG, not Strategy, created by Blizzard. Not related to the Warcraft Universe in any way, nor are there significant contributions from that universe to this one. Althought, there have been some rumors of more linkage.
Diablo I
The setting of Diablo I was the town of Tristram, the de facto capital of the Kingdom of Khanduras on the world of Sanctuary. The actual fighting took place beneath the town in maze of dungeons, catacombs and caves that led into the depths of Hell.
The plot of the original Diablo game centered around a player character undertaking a series of quests to free the Tristram from Hell-spawned evil, descending through twelves levels of dungeons, catacombs, and caves into Hell itself (the final four levels), where the player battled the title character, Diablo, Lord of Terror, one of the seven "Evils" (devils) who ruled Hell.
Users who played for plot had mixed reactions. For the first half of the game, there was no conception of what was happening if the user had not read the manual first. Conversely, most of the back-story in the manual and a wealth of other knowledge were available as in-game text. This attempt at immersion all but failed, however, due to the random nature of quests in the game. As the game was designed, only three quests- the Chamber of Bone, Archbishop Lazarus, and Lord of Terror- were included every time the game was played, the last two being the endgame. Hence, some interesting characters and texts were never found by some players.
Diablo I classes
Diablo I offered three character classes and the Hellfire expansion offered three more. Players would play as Warriors, Rogues (archers), or Sorcerers. Each class had their own place in the game's history, and all three classes were seen as NPCs in the sequel. All thee classes had the same general skills and access to the same spells (though the Sorcerer obviously had the edge there). Each of them had a class-specific skill (Repair Item, Disarm Trap, and Recharge Staff, respectively) that had as many drawbacks as benefits.
In terms of game mechanics, Diablo was a bit annoying in terms of what characters could do and the nature of items, many of which had penalties to offset the benefits (for example, a Unique helm found on level 14 boosted defense greatly, but reduced the light radius drastically).
Hellfire
The official expansion pack was started by Blizzard and then passed on to Sierra to finish. It offered an additional three character classes: monk, barbarian, and bard. The monk fought without weapons and little armor, because he had great natural damage and defense due to his martial arts expertise. The barbarian was similar to the warrior, except he had no magical ability. All his melee character statistics were higher to compensate. The bard was a weak character who had balanced statistics.
The addition of two bonus levels also angered many players because it took away from the game's gothic appearance- the first of these levels featured bizarre insectoid creatures who bore passing resemblance to the Silithid and the Zerg. The second level returned to demons, but they had nothing in common with Diablo and his minions.
Since it was finished by Sierra and not Blizzard (by their authorization), the information offered in Hellfire may not be part of Diablo lore. It should be noted that Hellfire does not appear on the lists of products on the website of either company (however this is due to it being out of print). It should also be noted that both Blizzard and Sierra are currently owned by the same company Vivendi (when Hellfire was made both were owned by Cendant).
Set up the sequel
Contrary to popular belief, the layout of the Diablo universe was well-designed in the original game, and intended sequels would have been centered around similar battles in Lut Gholein and Kurast to kill Baal and Mephisto, the brothers of Diablo. By providing the "seven devils" explanation and the identity of Tyrael the archangel early on, Blizzard ensured that sales would be the only barrier to a sequel. To preserve continuity, the sequel had Diablo surviving by possessing the hero who defeated him, so Diablo remained the antagonist of the second game.
Diablo II
Diablo II classes
Diablo survived the original confrontations by possessing the warrior who has defeated him, and set about freeing his brothers, Mephisto and Baal, the Lords of Hatred and Destruction, respectively. Players could choose from five (or in the expansion, seven) distinct characters to control in their quest, which explored the planet of Sanctuary through four acts. A different devil was the boss for each act, with Diablo at the end of the game, this time dying for good.
Diablo II broke several sales records and was hailed in an endless stream of good reviews as having the best plot for an RPG. Notably, it was also the first computer RPG to have a significant number of female players (more than 26%).
The character classes, in particular, were much stronger than the previous game's. While the Warrior, sorcerer and rogue remained slightly aloof, the new classes were clearly grounded in the world, and players were able to learn the motivations of all the classes, and why they were fighting this battle:
- The oracles of the Amazons foretold that the final battle, when mankind would at last be free of angelic and demonic manipulation was at hand.
- The Barbarians also expected a "final battle," in which they would be key players in deciding the fate of the world
- The Necromancers determined that the Evils had grown too powerful, and thus allied themselves with the forces of Light to restore balance to the world.
- The Paladins, wracked with guilt over their actions during the Inqusition, sought justice upon Mephisto, the true cause of the bloody crusade.
- The Sorceresses join the battle with their mighty spells to stop the corruption of magic by the Evils.
The characters from the previous game were not forgotten, however. The Rogues (as NPCs) were the hostesses of the player during Act I, and Sorcerers were seen regularly in Acts II and III. Unlike the original, each character had three distinct sets of skills/spells that s/he could use in the game. Several of the characters could also conjure magical minions, such as a Valkyrie (Amazon), Skeletons and Golems (Necromancer). All players also had the option to hire a Rogue (Act I), a warrior (Act II) or an Iron Wolf (a type of melee sorcerer, Act III) to accompany them and help slay monsters. These "hirelings" had a few of their own skills and could usually take care of themselves.
Lord of Destruction
The expansion set, in which players fought the army of Diablo's brother, Baal, further solidified the reputation of both game and company. The set included a new act, hundreds of new items, a deeper plot, etc. and two new classes, the Druid and the Assassin.
- The Druids are descended from the Barbarians, and have come out of hiding in preparation for the final battle between mankind and the Evils.
- The Assassins have policed the mage-clans for centuries. Now, with news that Terror and Destruction (Diablo and Baal) roam free, the Assassins unleash their fury on Hell itself.
Barbarians could also be hired in the new Act. The summoned units of the expansion characters are called "pets." Hirelings could be resurrected in Lord of Destruction and can be equipped with armor and weapons.
The "final battle" alluded to above is the player's confrontation with Baal and his armies in the fifth act. Let's just say that the ending is strange, but worth the price of admission.
Diablo III
Diablo II was certainly popular enough to spawn a sequel (and two Evils still live in Hell) and the likelihood that Diablo 3 will be made is very high. Admittedly Starcraft 2 and the second expansion to World of Warcraft are higher on Blizzard's priority list.
In spite of several clear lore difficulties, Diablo 3 has been the subject of discussion on many fansites. With the release of "Moon of the Spider" (see Novels, below), it appears that Metzen and the lore team do have a plan for the eventual return to Sanctuary, but as stated above, extensions of the Warcraft and StarCraft universes are higher on the list.
As of late September of 2007 there have been numerous statements made by Blizzard employees that they are working on 3 projects. The second expansion set to World of Warcraft as well as Starcraft 2 were both announced over the summer leaving one remaining unannounced project. In a recent interview with writer Richard A. Knaak, a question was posed to him that said the following:
"...In your last inteview you said, and I quote 'Im not writing for a dead game, but a game with dead, nuff said.' ... Do you have proof you are not writing for a dead game?"
To which he responded:
"I can only say that they will not forget Diablo. It's too popular a world, too rich a world, for them to forget. I can't say "IF", I gotta say "WHEN" ... they would do something, and that's all the extent of what I could say.
I am not writing for a dead world. I am writing for a World about the dead. The world is going to stay alive ... so to speak. (laughs)"
The entirety of the interview can be found: Here
Another bit of, of course, unconfirmed information involves the internal name for a Blizzard project that was allegedly overheard at a gaming conference. Apparently a Blizzard employee let slip that he was working on a project code-named 'Hydra'. Various interpretations have been made based on this generic name yet no conclusive statement can be made regarding its project's identity.
Novels
See Diablo Novels
Humorous references to Diablo
However, both Warcraft III and World of Warcraft do contains some in-game humorous references to Diablo, for instance, 
[Cow King's Hide] (Thottbot). Diablo II contained a secret level where one had to battle hordes of insane bovines, including the extremely powerful Cow King. This level was built into the game after a fake screenshot was posted of a secret cow level supposedly in the first Diablo game.
There's a saying in the loading screen/tips in World of Warcraft that says "There is no cow level".
Another common humor reference to the Diablo games is mention of Wirt, and his wooden leg. Wirt was originally an NPC character in the first Diablo game, filling both the role of a rare-item vendor, and a quest giver. It is believed Wirt was killed when Diablo's minions overran the NPC town of Tristram. In Diablo II, it was required to combine Wirt's leg with a Tome of Town Portal in order to gain access to the Secret Cow Level. In Warcraft III: The Frozen Throne, an item called "Wirt's other leg" could be found in one of the campaign levels after defeating The Butcher, a giant abomination named after an early boss in the original Diablo. Wirt's Third Leg (Thottbot) is an item available in World of Warcraft.
Influence on and differences from WarCraft
Humorous references aside, many spells and abilities in WC3 and WoW were inspired by skills in Diablo II, namely auras and the idea of passive skills. The RPG elements of Diablo were significant in the development of WoW, as it meant that Blizzard already had experience in building an RPG. Here are some of the similarities that players may notice between games:
- Barbarians featured a variety of buffs in the form of battle cries, which may have inspired the warrior's Shout abilities.
- Several of the mage's spells are taken directly from the sorceress, including Mana Shield, Fireball, Frost Nova, and Frost Armor.
- The rogue's combo point system is similar to that of the assassin's charge system in which players could accumulate charges and unleash finishing moves whose powers depended on the number of charges the player had. The assassin also featured a series of damaging traps.
- Druids from Diablo II could shapeshift into werewolves and werebears.
- Paladins in Diablo II had numerous auras. They also had the Charge ability, which now belongs to the warrior.
- The necromancers in Scholomance and Stratholme use the Bone Shield spell and can raise skeletons, both of which Diablo II's necromancers had.
- Socketed items were first introduced in Diablo II.
Like WarCraft, Diablo features demons, but unlike Warcraft, Diablo's demons are ruled by devils, come from Hell, and fight a war against actual Angels. The motivations of the demons are probably the same, but the more traditional nature of Heaven and Hell make the world of Diablo extremely different from that of Warcraft. Religion becomes a conflict (references are made to Mage Wars and Inquisitions), and humanity become pawns in a greater conflict between Angels and Demons. In the World of Warcraft, the fight for fame and glory can be tied in to a quest to save the world from the evils of the Old Gods or the Burning Legion. In the world of Sanctuary, no quest for prestige and riches can occur without facing the minions of Hell.