Just posted a smaller version of this in the Sargeras vs Old God post. But I'll go all out here.
Source: https://www.youtube.com/watch?v=-yat...outu.be&t=4m6sIs Archimonde really dead?
I can tell you our idea behind that. We might change it. This might not be canon. This might be something that we decide we're gonna tinker with. I'll try and explain what the thinking was. The idea was that the demons in the Burning Legion, they're kind of immortal in that they can exist across all the planes, unless they're killed in the actual Twisting Nether itself. So killing Archimonde at the World Tree in Warcraft 3... well, he was killed on Azeroth, but he would re-coalesce in the Twisting Nether and come back to haunt us again. And the idea was if you played in Mythic and defeated Archimonde, you actually defeated him in the Nether and that he'd be dead dead for good. That was the idea that we played with. We tried to explain that and I don't know if... that certainly doesn't come across in-game because it's not necessarily explained in-game. Maybe we'll change that. Maybe we'll change the canon of that. But that was the idea that we were working with... was unless you rip these demons out and take them to the Twisting Nether and kill them there, they'll always keep coming back. But maybe that's not canon. Maybe we'll tinker with that idea.
I know it's stated and even underlined that it isn't official canon yet but this is for the sake of discussion.
This has no doubt been discussed to death because it makes absolutely no sense and it still doesn't. There is one giant inconsistency with Blizzard saying that when Demons die, they return to the Nether until killed inside the Nether. Prior to the absolute Lore ravaging which occurred in Warlords of Draenor and the introduction to idiotic time travel, alternative universe nonsensical madness the only beings that resurrected as such were Dreadlords who were the only known confirmed Demons to actually return to the Nether on Death and certain Godlike beings such as Cenarius have returned also although apparently characters like Malorne and Agamaggan who both died in the War of the Ancients, Agamaggans bones are currently present in game in the Barrens and his Spirit is part of a quest in said Bones and hell even Sargeras after his body was presumably annihilated after the Well of Eternity imploded, although he is basically a God so his 'spirit' remained are oddly still physically dead or MIA. Strangely inconsistent.
Now the mention of Dreadlords is important, when they have died in previous games or in World of Warcraft their corpses vanish in a trail of bats and leave their armour behind and their souls or such return to the Nether. This unrelenting resurrection was also one of the causes of Sargeras' fall to madness because they were evil beings that simply could not be vanquished. Pretty consistent throughout all of Warcraft.
Now here's the one somewhat major flaw in the one Archimonde, one Demon across the entire Timeline Universe nonsense plot which makes it basically entirely nonsensical, hell it makes all of Warcrafts Lore nonsensical and utterly pointless.
This one flaw is Mannoroth the Destructor, Mannoroth is one of the Burning Legions most powerful lieutenants, he is one of Archimonde's and Kil'jaedens favourite enforcers and was even a spearhead of the Burning Legion in the War of the Ancients and thus one of the most powerful Demons currently known. Mannoroth in our Universe died, in his death the Orcs bloodrage totally subsided and Grom was hailed a Hero of the entire Orcish race. Currently his Skull and the entirety of his Corpse is being hanged in Orgrimmar for everyone to see. His bones were also worn by Garrosh in a set of badass Shoulderplates and his shattered weapon displayed in Ashenvale. Basically, Mannoroth died in our Universe.
Yet, apparently he returned in AU Draenor. He died in the cinematic and didn't disappear back into the Nether instead Gul'dan collected his bones and resurrected him back into form on our fight on Hellfire Citadel and it wasn't some Soul into Body shenanigans it was some total physical reconstruction because Pit Lords tend to explode when they die, although he didn't seem to dissolve into a pile a blood in our Universe as his entire corpse is on display. Basically, there are two Mannoroths. One in our timeline and one in AU Draenor.
Why is there apparently one Archimonde spanning across all the Timeline Universe's? It doesn't make any sense. One could argue that it could be a Pitlord trait, when Pitlords die they don't go back to the Nether. Well that doesn't really stay consistent in the fact that before you fight Archimonde in Hellfire Citadel you fight Anetheron, Kaz'rogal and Azgalor another familiar Pit Lord from the Battle of Mt. Hyjal. So apparently Azgalor, one of Mannoroth's lieutenants has this magical Nether resurrection ability whilst Mannoroth doesn't? Basically it's just inconsistent nonsense.
Another reason this whole thing is nonsense is because if you look at it, it has created a major dissonance problem with the whole Warcraft Lore. If there are infinite Demons and infinite Azeroths and infinite Draenors. This means that Kil'jaeden, Mannoroth and the rest of the Burning Legion could recruit an unlimited number of Iron Hordes. This makes the entire story completely and utterly nonsensical and pointless. They could just keep doing the Warlords of Draenor story over and over and over inf. again. This is why Timetravel and alternative universe nonsense should stay out of any storytelling and whenever it is included the story turns into absolute garbage.
Hell if there is only one Archimonde and he died in the past in a separate Universe then how was he in the future in order to do the entirety of the plot of Warcraft 1, 2 and 3? If Archimonde died in the past in the Nether then everything past that point would of changed and the entirety of Warcraft Lore on our Azeroth would be completely entirely different. Just think about that, what we are doing in AU Draenor is in the past and apparently we killed Archimonde for good...in the past.
Timetravel Alternative Universe stuff is total nonsensical garbage and shouldn't of happened. As a fan of the stories of Starcraft 1, Diablo 2, Warcraft 1, Warcraft 2, Warcraft 3 it really is upsetting to me what has happened to Starcraft 2, Diablo 3 and World of Warcraft because the previous games stories were actually incredible, some of the best in gaming in fact now they are a joke.
It has to be two Archimonde's. Being one spanning all timelines and universes is impossible without retconning everything in the entire Warcraft story, may as well go full Warhammer and destroy the universe at that point.