Diablo 3 Story: Almost 20 years have passed since Diablo has been cast away from the World of Sanctuary by a group of brave heroes. The Lord of Terror and two of his brothers, Mephisto and Baal were slain but many mortals have sacrificed their lives to save their homeland from the burning fires of Hell. The Archangel Tyrael was forced to break the sacred laws of the High Heavens and interfere with the mortal realm, destroying the World Stone beneath Mount Arreat. The sacred mountain was destroyed in the process, leaving the mighty barbarians without their homeland.
Before he was slain, Diablo managed to corrupt the powerful witch named Adria. Through his power he managed to conceive Leah, daughter of Adria. The little girl was abandoned by her mother but Deckard Cain, last living member of the other of the Horadrim took the child and raised her as his own.
While everyone was fooled into thinking that the Lord of Terror has been vanquished forever, a falling star brings shatters the night skies above old Tristram. The star falls through the old Cathedral where Cain was researching old prophecies. Dark days are coming as the forces of Hell are already on the move but the last of the Horadrim has foretold this moment. Tyrael himself chose to be a mortal due to the inaction of his brethren and fallen from the High Heavens in the form of that star. Unfortunately, the evil witch Magda kills Cain and attempts to stop Tyrael from helping the mortals but she is slain by a group of mortals.
During this time, Belial and Azmodan, the last two of the prime evils prepare their invading armies to march through the world of men. With the aid of Tyrael and Leah, a group of mortal heroes manage to forever vanquish the two demon lords. Unfortunately, Adria betrays them and captures the essence of the two demons into the Black Soulstone and surrenders Leah to Diablo. Once possessed by Diablo, Leah ascends to the High Heavens to end the eternal conflict and slay all angels. She is confronted by Imperious, the ruler of the holy heavens whom forces the girl to reveal Diablo’s true form. During their battle, Imperious is severely injured and forced to flee. Knowing that it was men who set Diablo lose into the High Heavens, the Archangel develops a hatred torwards the mortals.
Shortly after, Tyrael and the mortal heroes join the fight up in the holy skies and find the Heavens under siege by the forces of Hell. They start ascending and push forward to the find Diablo in the Crystal Arch. The mortals engage the demon lord and manage to slay Diablo. With the demon lord forever vanquished, the realm of men is now free from the wrath of the burning Hells. Tyrael returned to the High Heavens but as a mortal, and changing his name from Archangel of Justice to Wisdom. From this point onward, Archangels and men will stand together and confront their enemies as their strongest moment was when they fought side by side.