Warcraft

Warcraft is a game series created by Blizzard Entertainment. It is Blizzard's oldest mainstream game series, most expansive in terms of lore and in light of the financial success and spread of the MMORPG World of Warcraft, arguably its most successful. Originally, Warcraft was an RTS series though has since embraced an MMORPG format.

In terms of visual style, Warcraft is on the opposite end of the artistic spectrum from Diablo.

References to Diablo

 * Both Warcraft III and World of Warcraft contain some in-game humorous references to Diablo, for instance, the Cow King's Hide. 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". This is a reference to the Secret Cow Level. The Secret Cow Level did appear in WoW during the 20th anniversary of Diablo, complete with unique Diablo-themed rewards.
 * In reference to his demonic form in The Frozen Throne, one of Illidan's gag quotes is "Wings, horns, hooves...what am I saying, is this Diablo?"
 * Another common humor reference to the Diablo games is mention of Wirt, and his wooden leg. Wirt is an NPC in Diablo I, 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 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. Finally, Wirt's Third Leg is an item available in World of Warcraft.
 * Many spells and abilities in World of Warcraft are derived from 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.
 * s 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,, 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 features a series of damaging traps.
 * Just like in Diablo II, Druids possess shapeshifting abilities.
 * The Far Seer hero unit in Warcraft 3 can also summon spirit wolves like the Druid.
 * Paladins in WOW had numerous auras. The Charge ability of the Paladin from Diablo II also belongs to the WOW Warrior class.
 * The necromancers in Scholomance and Stratholme use the Bone Shield spell and can raise skeletons, both of which Diablo II's Necromancers have.
 * Socketed items were first introduced in Diablo II and later applied to World of Warcraft.
 * Diablo features an eternal war between the forces of the High Heavens and the Burning Hells. Warcraft has its own demons in the form of the Burning Legion and those who oppose them serving the Holy Light, such as the Naaru.
 * The Light carries the same name in both universes, and operates in much the same way, sanctifying paladins and uniting the people of Sanctuary (even Necromancers) or Azeroth (even Warlocks) against their common foes.
 * Demon Hunters in Diablo also play an important role in both Warcraft III and World of Warcraft.
 * The helm of the Lich King can be found in the of Diablo III.
 * Thunderfury is also a blade in World of Warcraft.
 * The War of the Ancients bears resemblance to the Mage Clan Wars.