Great Evils

The Three Prime Evils, as they appears in Diablo II.

"Seven is the number of the powers of Hell, and seven is the number of the Great Evils." - Vischar Orous

The Great Evils are the seven most powerful demons in the Burning Hells who were spawned from the seven heads of Tathamet. The three strongest are the Prime Evils, and the four others are the Lesser Evils. Each Great Evils rules over a specific domain of Hell that reflects their epithets.

Origin

Tahameth, the Prime Evil:

A seven-headed dragon composed of all darkness and vileness that Anu cast off itself before the universe was created. Not much is known about Tathamet but it is known that he was the only reason that The Burning Hells came into existence, also there is no record of him ever mating with another creature. Tathamet battled Anu, and when the two beings died the seven heads of Tathamet became the seven Great Evils. The three most prominent heads became Diablo, Mephisto and Baal, and the four lesser heads Azmodan, Belial, Andariel and Duriel. Tathamet's body meanwhile became the foundation for the Burning Hells.

Prime Evils

The Prime Evils are comprised of the Three - the Demon Lord brothers and absolute rulers of Hell:

Diablo, the Lord of Terror:

Younger of the Three, strongest prime evil and main antagonist of the Diablo-series. Mostly long and mid range fire attacks.

Mephisto, the Lord of Hatred:

Eldest leader of the Three, Father of Lilith and Lucion. Specializes in mid range lightning attacks.

Baal, the Lord of Destruction:

The most insidious and ruthless of the Three. Usually considered to be single-minded. Specializes in all attributes.

History

The three Prime Evils, also known as the Three or sometimes the Brothers, led the forces of the Burning Hells against the High Heavens for countless eons from the beginning of time. They were spawned from the Three main heads of Tathamet, and their domains -- hatred, terror and destruction -- fuel each other and thus fuel the Prime Evils themselves. This ensured their rule over Hell for countless eons until the time of the Dark Exile.

Despite their power, the Three were eventually ousted from Hell by the Lesser Evils, led by Azmodan and Belial. It required the minions of the Three to turn on their masters as well before they could be banished, and before the war was over one third of Hell's denizens had been destroyed by the Prime Evils. The Three were defeated and banished to Sanctuary.

Nine years after Baal was buried in Aranoch,, 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.

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,

Once Baal was free he had access to the knowledge and power that Tal Rasha had possessed in life, chief among them the location of the Worldstone. Baal was seeking it, inside the innards of Mount Arreat. However, Baal is defeated and the Worldstone is destroyed by Tyrael, due to Baal's corruption of it.

After Baal defeat, all of the Prime Evils have been banished to the Black Abyss.

The Prime Evil

The Prime Evil was the combination of all the Great Evils into one being. Twenty years after the Prime Evils's defeat, the witch Adria who had been in league with Diablo had search for the Black Soulstone and confined the essence of the 5 Great Evils (Diablo, Mephisto, Baal, Andariel and Duriel) into the Soulstone. Diablo had engineered a plan to finally defeat the High Heavens once and for all. While he was gaining control over Aidan's mind, Adria and Aidan (Diablo) had been romantacly involved and had conceived a daughter named Leah. The last Lords of Hell Azmodan and Belial soon began their invasion of Sanctuary in search for the Soulstone with Belial taking control of Caldeum while Azmodan began mustering his forces on Mount Arreat. A group of heroes under the guidance of Adria, Leah and Tyrael resurrected the renegade Horadrim mage Zoltun Kulle the creator of the stone, who show them where the soulstone was. The heroes soon defeated Kulle who turned against them and took the Soulstone, they liberated Caldeum from Belial and finally confronted the Lord of Lies and confined his essence. The heroes soon turned their gaze on Azmodan, who began his invasion from Mount Arreat, after a long fight against his armies the heroes confronted Azmodan and battled with the Lord of Sin, they were victorious and Azmodan's essence was confined into 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 he shattered the Diamond Gates with the intent of corrupting the Crystal Arch. The heroes battle against the Prime Evil and defeated him, saving Sanctuary and the High Heavens. However, they were unsure if the Great Evils had been truly defeated.

Rulership

It is unclear which, if any, of the Prime Evils leads. Though it is never stated outright, Diablo has been generally assumed to be the foremost of the Three. This is stated in Diablo I (by Lazarus) in the tome Tale of the Three, and hinted at by Auriel in The Veiled Prophet. The Book of Cain, however, hints that Mephisto is most deserving of the title.

The Brothers have over the span of the games often worked closely together and without any apparent sign of discord between them. This is strictly opposite to what we've come to know of all other demons, who constantly vie for power at the expense of their other brethren. Traditionally this has been held to indicate that the Three have been above such squabbling amongst each other, however when talking to Inarius Diablo gives another impression:

"I deal with a traitor, a liar, and a murderer, said a voice that, despite Inarius’ claim, sent a slight chill through him. It’s almost like dealing with one of my brothers."

It remains to be seen how the relationship between the Three has worked in the past.

Lesser Evils

The Lesser Evils are second only to the Three:

Duriel, the Lord of Pain

Twin brother of Andariel. Though Duriel had his part in the Dark Exile, he has once again aligned with the Three. Sent to guard Tal Rasha's Chamber. Specializes in heavy melee attacks and uses ice as an aura.

Andariel, the Maiden of Anguish

Twin sister of Duriel. Sent to guard the Rogue Monastery by Diablo himself. Specializes in mid range poison attacks.

Belial, the Lord of Lies

One of the leaders of the rebellion against the Three. Brother and rival of Azmodan. Uses fire for both phases of his fight with heroes: on the 2nd phase, he'll dig his massive claws into the ground, breathe huge gusts of fel flame and make feiry erruptions.

Azmodan, the Lord of Sin

One of the leaders of the rebellion against the Three. Brother and rival of Belial. Throws fire boulders, summons demon gates to call upon minions and call forth dark magic in a large AOE.

History

Despite the name, the Lesser Evils are far from weak; they are only lesser in comparison to the Prime Evils. There are four known Lesser Evils, and they were spawned from the remaining four heads of Tathamet. Though historically they answered to the Prime Evils, the Lesser Evils each reigned over their own territories of Hell and served as demon lords to their own demonic minions.

These four overthrew the Brothers and banished them to Sanctuary, where they were subsequently hunted down and imprisoned within the Soulstones. Azmodan quickly wrested control of Hell from the other three Lesser Evils, and it is unknown what he did with his defeated allies. They did all survive until the Prime Evils returned and both Andariel and Duriel traveled to Sanctuary to aid the Prime Evils in their quest.