Diablo,El Señor del Terror.
Mefisto,El Señor del Odio.
Baal,El Señor de la Destrucción.
These are the Prime Evils of Hell that wielded their power as a dark, sovereign triumvirate, spawned from the dominant heads of the Dragon Tathamet. The Three Brothers ruled over the Lesser Four by brutal force and malicious cunning. Being the eldest and strongest of the Evils, the Three Brothers were responsible for many victories against the armies of the Light, and served as the "eternal adversaries" of the five ruling Archangels of the Angiris Council. Although even they were never able to breach the Diamond Gates of the High Heavens, the Three were justly feared by enemies and subjects alike.
In the original Diablo game, the strongest Prime Evil, Diablo, was captured by the Horadrim and imprisoned inside a soulstone. Diablo was then buried deep beneath caverns under the town of Tristram. The main story line of Diablo I follows on from there.
After his defeat, Diablo seemed totally banished, but his presence was eventually made manifest inside the mind of the hero who defeated him. Slowly, the hero who slew Diablo was corrupted and driven by Diablo to seek out his two other brothers: Mephisto and Baal. The game Diablo II is where the story picks off from Diablo I, with the player playing a pursuing adventurer, trying to stop Diablo and prevent him from reuniting with his brothers. In the proceedings of Diablo II, Mephisto is defeated and his soulstone is destroyed. Eventually, Diablo himself is defeated and his soulstone is destroyed as well. However, the storyline leaves out what happened to Baal, the third brother, and thus, Diablo II is extended by an expansion pack: Diablo II: Lord of Destruction to explain what happens to Baal.
The expansion pack, Diablo II: Lord of Destruction's storyline introduces a new mythical object into the Diablo Universe, the Worldstone, which is an ancient crystal-rock that exists to prevent the Heavens and the Hells from completely enveloping the mortal realm into their respective folds. Baal is seeking it, inside the innards of Mount Arreat. However, true to the games preceding it, Baal is defeated and the Worldstone is destroyed due to Baal's corruption of it.
As of the end of Diablo II: Lord of Destruction, all of the Prime Evils have been banished to the Black Abyss.
Diablo en su próxima aparición en Diablo3.