Interesting. I could’ve sworn it was a prominent thing but it could be something speculated. Here’s what I could find from Tides of War:
Instead, there was a violet glow, almost pretty, like moonlight on snow, emanating from the city. And above that deceptively pleasant radiance, the sky was putting on a show. Bright spikes of lightning slashed through the blackness in all colors of the rainbow. Here and there, the jagged illumination lingered, moving and turning only to wink out and reappear elsewhere. They were close enough to hear booming and cracking sounds as the very fabric of the world was again and again rent asunder and knitted together. (p. 222)
The soft purple glow heralded the blanket of arcane energy that enveloped Theramore. The mana bomb, so thoughtfully provided by the blood elves—who stood cheering with other Horde members who somehow felt that what Garrosh had wrought was a good thing—had exploded over an entire city and had not just harmed its citizens and buildings but crushed them utterly. Baine had watched both friend and foe perish from arcane magic attacks far too often to feel anything but fury at what he beheld. The people caught in the blast had been blown apart inside, as magic distorted and reformed them down to the last drop of blood. The buildings, too, were remade from the inside. So great had the blast been that Baine knew that every creature, every blade of grass, every handful of soil was now rendered dead and worse than dead. And the awful magic would linger. Baine did not deal with magic. He did not know how long the eerie violet glow that marked Garrosh’s calculated brutality would pulsate around the city of the slain. But Theramore would not be livable for a long time. (p. 223)
Morning was unkind to the ruins of Theramore. Without the gentling of the darkness, the stark devastation was blatant. Smoke still curled upward from the mostly dead fires. The arcane anomalies that had provided a show of lights at night were revealed to be evidence of realities and dimensions ripped asunder. One could even glimpse other worlds. Hovering in the air were not only rocks and chunks of earth that had been torn free, but the debris of buildings and weapons. Bodies turned slowly in the air, like grotesque puppets floating in water. The crackling and thundering were ceaseless. (p. 225)
Something interesting I found about the Focusing Iris is that it’s related to the Twisting Nether?
It was previously mentioned that once harnessed, the energies are focused through the Nexus’ ascending rings and blasted into the Twisting Nether. In Thrall: Twilight of the Aspects , this function of the Nexus is not mentioned. It is implied that the diverted energies were stored there.
https://wowpedia.fandom.com/wiki/The_Focusing_Iris
Also Surge Needles are related to the Iris:
Surge needles are massive constructs that aid in the redirection of ley lines for Malygos
https://wowpedia.fandom.com/wiki/Surge_needle
Malygos had used his own blood to activate and control this orb, which had lain dormant for millennia. With the open Focusing Iris, Malygos had been able to direct (and create[4]) powerful surge needles, using them to pull arcane magic from Azeroth’s ley lines and channeling that magic into the Nexus.
https://wowpedia.fandom.com/wiki/The_Focusing_Iris#:~:text=short%20stories.-,Malygos,-had%20used%20his
And it seems that Surge Needles have the ability to tear into dimensional space into the Twisting Nether:
The Ethereum seeks to become an unstoppable force–to become void,[1] and they are using the surge needles in Coldarra to bore into the Twisting Nether and call up void energies
https://wowpedia.fandom.com/wiki/Ethereum
Some info about Arcane and it’s impact on reality and space/time:
Arcane magic (also called Order magic, arcane energy, or arcana) is a cold and intellectual magic that warps time, space, and controls the flow of mana, which is just a measure of a fundamental power—if mana were water, then arcane would be steam pressure. Though extremely volatile, arcane is so similar to an element it might as well be one, for all magical intents and purposes. As the manifestation of Order in the Great Dark Beyond and the Twisting Nether, arcane is the language of order and the opposite end of the spectrum from fel, which represents Disorder.
https://wowpedia.fandom.com/wiki/Arcane
The text seems to be quite clear that the destruction was something that was worse than death itself. The ‘reality’ of the impact zone is in a constant state of being torn apart and reconstitution which would imply perpetual destruction ‘for a long time’.
There’s also mention about glimpses to other worlds, so I believe this might be where this ‘timeline’ thing came about. What exactly does ‘evidence of realities and dimensions ripped asunder’ and ‘one could even glimpse other worlds’ truly mean? I think this is where we enter speculation.
I’m assuming here that if the bomb is an allegory to the atomic bomb, and the impact zone is akin to a nuclear fallout zone, we would then need to also see it as an Arcane fallout zone where there the rules of arcane magic would have to be followed.
I also went to search where this information might have originated from and found this:
https://www.reddit.com/r/wow/comments/56msdp/comment/d8km6e1/
I believe most of the information are correct, and those in quotes can be found. The part about the timelines is the posters own write-up with a broken link. Which is understandable given its 8 years ago.
So I think this should be classified as a theory rather than something official because there’s no clear understanding of what things like “realities and dimensions ripped asunder” and “glimpse other worlds” truly means. It could range from something in a localized context as the destruction is on such a fundamental level that even their souls cease to exist (but this would be more inline with Fel rather than Arcane?), to some weird atomic destruction where the atoms are in flux and doing weird things, to some sort of weird dimensional twist related to the Twisting Nether, to realities as in every reality in existence at the point where the arcane fallout occurred (as in that point of space/time is irrevocably damaged?)
