Diablo arrived at the Diamond Gates of Heaven wearing Leah's form, but Imperius, the Archangel of Valor and commander of Heaven's forces, saw through the illusions of his ancient enemy, and scorched the demon's false visage away.

Diablo's true, terrible form was revealed, and the two fought bitterly until Diablo defeated Imperius and shattered the Diamond Gates. While Hell's forces had besieged Heaven many times, they had never before managed to breach its gates—until this moment.

Once the Gates fell, the remaining members of the Angiris Council, Heaven's angelic leadership, were swiftly scattered.

Rushing to halt the despoiling of Heaven, Tyrael and the nephalem pursued Diablo through the open portal. There, they encountered a wounded and defeated Imperius, who blamed them for the ascension of the Prime Evil and the ruination of the High Heavens.

Diablo's desecration of Heaven had been merciless. Scores of Hell's most powerful, avaricious demons flooded through Hell Rifts. Angels were twisted into demons. Despair gripped the legions of the Heavens.

Undeterred, the nephalem fought their way through the conquered High Heavens—seeking the guidance of Itherael, Archangel of Fate, and rescuing Auriel, Archangel of Hope—before ultimately confronting Diablo atop the Crystal Arch, the source of Heaven's power and the lifeblood of all angels.

Empowered by the souls of the Evils, Diablo unleashed ceaseless horrors upon the nephalem, even drawing them into his reality-warping Realm of Terror.

But the nephalem succeeded where the forces of the High Heavens could not, and, after a titanic conflict, finally rent Diablo's physical manifestation into ash.

With Diablo vanquished, the hosts of the High Heavens set to rebuilding the ruin of their home.

Tyrael rejoined the Angiris Council as the mortal Aspect of Wisdom—a quality he knew would be sorely needed in the days ahead. He strove to heal the pain and distrust that spread through Heaven in the wake of Diablo's invasion, and to forge a true alliance between angels and mankind...

...but the specter of the Eternal Conflict continued to loom over his hopes for unity.