Diablo Immortal sits somewhere in the middle of the Diablo story timeline. The new game is hence both a sequel and a prequel.
It remains to be known if the events of Diablo Immortal will go on to somehow affect the setting of Diablo 4. They are understandably still important enough to affect the main timeline nonetheless.
The following walkthrough will explain where and how Diablo Immortal sits in the timeline.
Understanding Diablo Immortal Timeline
Diablo Immortal takes place between the events of Diablo 2 and Diablo 3. It acts as a bridge to fill the two-decade gap in the timeline between the two games.
According to the available lore, Diablo Immortal takes place just five years after the events of Diablo 2 and 15 whole years before the events of Diablo 3.
It hence becomes important to first recap what happened in the earlier Diablo games and how Diablo Immortal sets up the events of Diablo 3.
What Happened In Diablo 1
The first Diablo game had a relatively straightforward storyline. Following a demonic invasion of Tristram, an unknown hero dubbed the Stranger (and later the Dark Wanderer in Diablo 2) stepped up to defeat Diablo, the Lord of Terror and one of the three Prime Evils.
In the Diablo games to follow, the Stranger was revealed to be Prince Aidan, the eldest son of King Leoric who had been driven mad by Diablo.
Aidan, however, had only one way to permanently defeat the Lord of Terror. After containing Diablo within a Soulstone, he plunged the Soulstone into his own forehead in a bid to contain Diablo and stop his essence from escaping his prison.
What Happened In Diablo 2
Diablo 2 took place right after the events of the first Diablo game. The Lord of Terror was simply too powerful. From within the Soulstone, Diablo managed to possess and control Prince Aidan to free his brothers and the other two Prime Evils: Mephisto, the Lord of Hatred; and Baal, the Lord of Destruction.
Prince Aidan, the hero of the first Diablo game, became the Dark Wanderer in Diablo 2 due to his corrupted state.
Thankfully, a new hero stepped up to defeat the Dark Wanderer as well as the Prime Evils. However, not before Baal managed to corrupt the Worldstone, an ancient object that holds the power of creation and is believed to have created Sanctuary itself.
In its corrupted state, the Worldstone threatened to corrupt and destroy all of mankind. The threat forced the archangel Tyrael to descend from the heavens to destroy the Worldstone in a massive explosion.
What Happened In Diablo Immortal
Diablo Immortal has only been released and its storyline is yet to be fully revealed. The lore itself remains to be updated.
What is known, however, is that the explosion at the end of Diablo 2 scattered shards of the corrupted Worldstone across the world. The peace that was won at the end of Diablo 2 was hence short-lived.
The shards of the corrupted Worldstone have risen a new demonic threat. There are cultists looking to find and harness the shards to open a gateway to bring about the return of Diablo.
As Blizzard Entertainment put it, these shards are like pieces of uranium. Their radioactivity is not only feeding demons to become more powerful but also slowly corrupting the lands of Sanctuary.
Diablo Immortal is hence all about containing the shards of the corrupted Worldstone.
What Happened In Diablo 3
Sanctuary was somehow saved at the end of Diablo Immortal and mankind enjoyed a long era of peace. That peace was then broken when the archangel Tyrael fell from the heavens to warn about the arrival of two of the four Lesser Evils: Belial, the Lord of Lies; and Azmodan, the Lord of Sin.
Like the first two Diablo games as well as Diablo Immortal, Diablo 3 introduced a new hero who would go up against the Lesser Evils. The hero would be a Nephalem, an offspring of an angel and a demon.
Both Belial and Azmodan were eventually defeated by sealing them inside the Black Soulstone (not to be confused with the corrupted Worldstone) but not before the Black Soulstone was used to resurrect Diablo.
In the end, the Nephalem was able to defeat Diablo but to no avail. The Black Soulstone was destroyed and hence, the essence of Diablo as well as the other Evils within were all released. Furthermore, just like with the Worldstone, shards of the Black Soulstone are now scattered across Sanctuary and threaten to release all the Great Evils upon mankind once more.
What Happens In Diablo 4
Diablo 4 is a long way out and hence, no one really knows about its storyline.
What is known is that Lilith, the daughter of Mephisto and the Queen of the Succubi, has been released from her prison. Lilith is also the mother of the first Nephalem after her forbidden union with the archangel Inarius in the lore. She is believed to have been released by Rathma, a first-generation Nephalem.
The shards of the shattered Black Soulstone are also likely to play a major role in the storyline with presumably a new hero taking on the mantle against the new threat to Sanctuary.
