The Three Prime Evils—from left to right, Baal, Diablo and Mephisto
The term Prime Evil is one that has been applied to various demons of Hell, whether it be a single Prime, or the three brothers.
History
Anu and Tathamet
Sins beget sins as men beget men. Terror begets Hate and Hate begets Destruction.
The Guhawj Cave Inscriptions (repeated multiple times).[1]
At the beginning of time, there existed a single, perfect entity called Anu. Anu desired to purify itself of all darkness and cast out its darker half. This dark essence congealed and formed the seven-headed creature called Tathamet. For aeons, Tathamet and Anu battled against one another until they unleashed the totality of their power. In the end, both were vanquished, leaving only their fractured essence behind.
As Tathamet's body formed the foundation of the Burning Hells, each of its heads became a greater demon. The three dominant heads became the Prime Evils, while the remaining heads became the Lesser Evils. The three Prime Evils collectively established themselves as the leading power among the Burning Hells. These were Diablo, Lord of Terror, Mephisto, Lord of Hatred and Baal, Lord of Destruction. They endeavoured to maintain a strict rule over the demons of Hell, each powering one another—as terror leads to hatred, hatred leads to destruction.[1] However, their unity was fragmentary at best[2] and while Mephisto was effectively the de facto leader, he would pit his brothers against one another if it suited his purposes.[1]
The Great Conflict
As Tathamet had given rise to Hell and its rulers, so too had Anu given rise to the High Heavens and the Angiris Council. The result was the Great Conflict, fought over the Worldstone.[1] 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.[citation needed]
The Sin War
The world was young, then, and only a few knew it as Sanctuary, or knew that not only did angels and demons exist, but some of them had caused Sanctuary to be in the first place. The names Inarius, Diablo, Rathma, Mephisto and Baal—to name a powerful and often dread few—had not yet been whispered on mortal lips.
From the Books of Kalan, First Tome, Second Leaf[3]
The Great Conflict came to an end when the Worldstone mysteriously disapeared. Millennia later however, the Prime Evils would discover what the stone had been used to create—Sanctuary. Thanks to the Vizjerei, Mephisto, Baal and Diablo were made aware of the existance of humanity. Sensing the latent power of the nephalem within them, they reasoned that if turned to their side, Man might make a powerful ally. So it was that the Three founded the Triune, adopting the namesakes of Dialon, Spirit of Determination, Mefis, Spirit of Love and Bala, Spirit of Creation. The angel Inarius, seeking to counter the influence of the Three, founded his own religion, thus beginning the Sin War.[1]
Future Events
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.
Prime Evils
The Prime Evils comprise the Three - the Demon Lord brothers and absolute rulers of Hell:
Diablo, the Lord of Terror is the youngest brother. He was responsible for the enslavement of mankind with violent images of bloodlust and terror; his prime weapon being the victim's fear. He was originally defeated under the labyrinths beneath Tristram but corrupted the hero who slew him and sought out his brothers, but then was defeated in Hell, by the pursuing adventurer. Mostly long and mid range fire attacks.
Mephisto, the Lord of Hatred is the eldest brother. He was originally captured by the Horadrim in the deserts near the city of Lut Gholein, the same place in which Baal was captured. He was moved to Kurast and imprisoned inside a Soulstone, and was kept locked inside the Guardian Tower beneath the temple city of Travincal. His eventual corruption of the regional religious heads almost ensured his release, except he was eventually defeated by the pursuing adventurer. Being the Lord of Hatred, he is the most intensely evil brother, whose greatest weapon is his victim's irrational hatreds. Specializes in mid range lightning attacks and close range poison attacks.
Baal, the Lord of Destruction is the last brother in the storyline of the Diablo games to be vanquished, and also the middle brother. Was the only brother to escape the pursuing adventurer. He raised an army of demons and minions and attacked the barbarian homelands of the north, laying siege to the capital city, Sescheron, and finally besieging the last city, Harrogath. He was stopped by the pursuing adventurer and eventually defeated. Specializes long range ice attacks and creating Illusions of himself.
The Prime Evil
Diablo, The Prime Evil
The Prime Evil was the combination of all the Great Evils into one being. Twenty years after Baal's defeat, the witch Adria who had been in league with Diablo and sought the Black Soulstone. With it, she was able to contain the essences of five of the Great Evils (Mephisto, Baal, Diablo, Andariel and Duriel).
Diablo had engineered a gambit to finally defeat the High Heavens once and for all. While he was gaining control over Aidan's mind, he conceived a daughter with the witch Adria, named Leah. Twenty years later, the last Lords of Hell Azmodan and Belial began their invasion of Sanctuary in search for the Black Soulstone with the intent of becoming the Prime Evil themselves. Belial took control of Caldeum while Azmodan began mustering his forces at Mount Arreat. A group of Nephalem heroes under the guidance of Adria, Leah and Tyrael resurrected the renegade Horadrim mage Zoltun Kulle, the creator of the Black Soulstone, to complete it. The heroes were forced to battle the traitorous Kulle, who attempted to use the Soulstone for himself and reign over Sanctuary. They later liberated Caldeum from Belial and finally confronted the Lord of Lies and captured his spirit. The heroes then turned their attention to Azmodan, who began his invasion from Mount Arreat. After a long fight against his armies the heroes confronted Azmodan and battled the Lord of Sin. They were victorious and Azmodan's essence was captured by the soulstone. Adria soon betrayed the heroes and performed a ritual to use Leah as Diablo's vessel. Diablo and his forces assaulted the High Heavens and shattered the Diamond Gates with the intent of corrupting the Crystal Arch. The heroes battle against the Prime Evil and defeated it, saving Sanctuary and the High Heavens. However, they were unsure if the Great Evils had been truly defeated.
Excerpt from the Tale of the Three
"Glory and Approbation to Diablo - Lord of Terror and Leader of the Three."
My Lord spoke to me of his two Brothers, Mephisto and Baal, who were banished to this world long ago. My Lord wishes to bide his time, and harness his awesome power so that he may free his captive brothers from their tombs beneath the sands of the East. Once my Lord releases his Brothers, the Sin War will once again know the fury of the Three."