The story of Diablo II begins with a new hero which will be one of five new types. The Amazon, the Paladin, the Sorceress, the Necromancer and the Barbarian. All the characters will have their own set of fighting abilities or spells. Diablo II will have four acts, which take place in four different locations. The locations are presented in a linear progression across the distant lands to the East, each accessible only after the final quest of the previous act is completed. Following the completion of the act, a caravan or a ship or some such conveyance becomes available and the hero can travel back and forth among the lands each route reveals.

Rather than having a single town the hero may return to, there is a different one in each Act (for a total of four), each with a unique flavour, and populated by new folk. Additionally, in each of these locations, there will be various dungeons, keeps, and caverns matching the theme of the area.

Act 1 : The Sightless Eye

Locations: The Steppes & the Frozen Lands

Not too far distant from the ruined Tristram, in the forested foothills of the great mountains, stands the great Monastery of the Sisters of the Sightless Eye. The Monastery, built into the sheer rock face of the frigid mountain, is a citadel protecting the mountain pass from the Western Empire to the mysterious east. In this boreal kingdom, walls of gelid granite and tall coniferous forests set off the rocky steppe. Caves might lead to the dens of whatever animals have braved this harsh environment. The Sisters of the Sightless Eye is the order that the rogue of Diablo was a member.

By currying favour with the Three, Andariel, one of the Lesser Evils, hopes to win a place at their side when they achieve ascendance. To this end, Andariel has attacked the Monastery and is using its underground passages for her evil deeds. In the attack on the Rogue Citadel, many of the Sisters of the Sightless Eye were captured. Andariel plans on killing her prisoners in a foul and horrific ritual which will turn the sisters into demonic entities. Only you can stop Andariel’s evil plan. Only after Andariel is defeated, will a caravan leave for the Broken Lands, allowing the hero to progress to the next act.

As the new hero, you will then continue on an epic journey across Demon infested deserts and jungles. Along this journey you will find out what happened to the hero from Diablo after he or she wandered to the east. In Diablo II , the terror that you will encounter is multiplied, as you must ultimately face Mephisto and Baal to rid the world of their demonic evil.

What has gone before :

Izual and his Angelic Runeblade Azurewrath were captured during his assault on Hellforge. Mephisto tortured Izual, and learned of the Soulstones being created by the Angels. He gained insight into the mystical properties of the Runesword, the Crystal Arch and the Soulstones.

The Sin War :

The greater lords of Heaven and Hell found that their powers were greatly reduced while in the Mortal Realm. They are limited in the amount of power they can draw and unleash into the mortal realm from their respective home realm (the source of their greater powers). They learned that the soul energy of their human allies and worshippers could be used as a source of energy, not only in the Mortal realm but in other realms as well. Dominance of the mortal realm would allow the controlling side to harness these energies from human souls (while denying the opposing force from access to this vast source of power) and grant them an edge against the enemy in the Great Conflict. Thus, the forces of Heaven and Hell began to struggle for control of the mortal realm with human souls as the prize.

Izual, who had by now fallen into the Darkness, suggested that the Soulstones might be manipulated by the Three in order to channel great amounts of power from Hell directly into the Mortal realm, allowing the forces of Hell to seize control. In order to gain possession of the Soulstones, the Three lure the Angels into using the Soulstones against them. Realising that a direct incursion by the Three into the Mortal realm might lead to a great confrontation between the forces of Heaven and Hell that had every chance of destroying the Mortal realm, the Three secretly manipulated the events leading to the Dark Exile.

By allowing themselves to be exiled in spirit-form, therefore appearing as a lesser threat, the Three set the perfect stage for the use of the Soulstones against them by the forces of Heaven.

Learning that the revolution in Hell was set into motion by aggressive Demon-Lords, frustrated by the standstill in the Great Conflict, the Angels were certain that a mass assault upon the realms of Heaven by the forces of Hell was imminent. In preparation for the attack, the Angels withdrew their forces from the Mortal realm, leaving mankind to fend for itself. The Angels of Heaven felt that the mankind's defence of their own world would be a way to prove themselves as worthy allies or a liability in the Great Conflict.

Although placing their main focus on the defence of their realms, the Angels of Heaven could not ignore the opportunity that was present to capture the Three within the Soulstones. Thus the Arch-Angel Tyrael bestowed the three Soulstones and their secrets upon the Horadrim, an order of mortal magi.

Events seemed to be proceeding as the Three had planned. Yet, in their overweening pride and overconfidence, the Three failed to consider the loss of strength incurred by their exile in the Mortal realm. The Three had laughed at Izual's warnings that they might become weakened enough to be at risk, sure in their arrogance that no Angels could ever overcome them even in such a state.

Without a physical vessel to contain their spiritual-form, they found themselves unable to hold onto the vast supply of energy from Hell. They found that the mere act of manifesting in the Mortal realm required heavy expenditures of energy. Steadily losing power and severed from their greatest source of energy, the Three were forced into possessing mortals prevent the further waning of their power.

The amount of energy a mortal vessel held seemed to vary depending on the strength of the mortal's mind, body and spirit: The greater his strength, the more could be held. The possession warped the physical form of the human vessel into a hideous parody of each of the Three's own demonic physical appearance.

The Three ravaged the lands of the mortal realm gorging, on human souls to rebuild their power. When Mephisto was finally hunted down and trapped within a Soulstone, he was not strong enough to warp it for his own use and too weak to even break free.

Baal during his encounter with the Horadrim managed to shatter the Soulstone before it could be used against him. However the battle left Baal weakened and forced to flee. Diablo and Baal surmised that though the shattered Soulstone might no longer be strong enough for what the Three had originally intended. They decided instead to return to hell, once there to draw upon the Energies of their realm to rule again and lead the hordes of Hell to utterly destroy the Mortal realm. Baal and Diablo then went their separate ways to re-gather the energy needed for this task.

When Baal felt he was powerful enough he confronted the party of Horadrim mages in possession of a Soulstone fragment, and who were hunting for him. Tal Rasha, an initiate of incredible will and magical power, led the Vizjerei, a group of Horadrim mages. Baal allowed himself to be drawn into the fragment of the Soulstone so he might attempt to twist it to his use. However Tal Rasha then bound Baal with his own soul by using himself as an extension of the Soulstone. Now a living Soulstone, Tal Rasha insisted he be buried and bound in the depths of a tomb beneath the great desert, the location of which was to be forgotten for all time.

Diablo was finally captured in the West by the Horadrim and also found in his weakened state to be unable to break free of the binding of the Soulstone. Over the years Diablo constantly tested the bounds of his imprisonment, slowly twisting the Soulstone to his needs. Like a slow malignant cancer he spread his evil presence into the Stone, warping its nature.