It was the Runecarver
The Primus had powers from an “unknown ally” that could allow him to see infinite timelines and thus win the battle
If such was the case I think it’s possible the Runecarver is the Primus and allowed himself to be caught because this was the only timeline where he eventually was freed and zovaal defeated
If vashj dying and Vashj seeing the primus is any indicator it is that the Primus was still around when Frostmourne was crafted.
The shadowlands and time has been likened recently to that of a dream and time, in a dream you might see a clock that says “it is 07:40 AM” and then you wake up and it is actually 05:00am, yes there is the Salanar quote etc. But that is still the case of a dream, you might be dreaming something that feels like 16 hours (and probably is in the dream) but in reality it is a couple of hours.
Anyway Vashj cant be in the shadowlands while Frostmourne wasnt in azeroth, That is a plot black hole in stupidity.
Same could be said of the other azerothian Maldraxxus souls. If any of them was present in Maldraxxus when the primus was there then it makes no sense. most of the known souls was there (bar kelthuzad and draka) was there after arthas got Frostmourne.
Oooo I like both your thinking! This lore is becoming more and more fascinating than that of D&D and Might & Magic! Its so similar but such a good new twist! LOOOOOVE IT!! 
Thing is we (myself included) only think Vashj met the Primus because she recognizes the runeblade as “of the Primus’s make”
It could be she just studied the Primus and his history.
Vashj’s timeline is a good point but knowing Blizzard I wouldn’t be surprised if they just forgot when she died. Never doubt these writers’ incompetence.
I really dont see how the cinematic even implies that the runecarver is the Primus.
The primus is a smith sure, but he also has many who learned from him.
Actually wont go into that because it would just become a bigger headache but it is regarding Zovaals need for an army, (and seeing as how that army would probably become this big after the arbiter stuff, and with it happening during legion… the timeline doesnt really add up)
I hope not. It was bad enough that Azeroth is the most powerful Titan/the #1 prize of the Burning Legion since its inception. I might just vomit if it turns out all the realities across Warcraft’s cosmology are after the same stupid planet.
Azeroth is like a living dopamine battery at this point. Given the reactions (in story) to Azerite.
I’m telling you guys: Arthas is the Runecarver and this is some good old fashioned Legacy of Kain temporal hijinks. We’re hearing the Lich King’s voice before the Lich King is even made.
On the logic that ~runes~ and ~runeblades~ so far are attributed to the Primus, the Blade of the Primus resembles Fromstmourne, Maldraxxus is the origin of all Necromancy in reality and thus is the Helm controls the undead, it’s tied to Maldraxxus by necessity
But… how did he get so tall and twinkish…
How did we turn Frostmourne into two swords that require more metal than Frostmourne had to begin with?
Magic.
I may have missed something. Where was it confirmed that the Runecarver is the Primus?
It’s not. We have nothing concrete to work off of. People think it’s the Primus because he disappeared and was the best runesmith in Maldraxxus. I admit that it’s some good evidence, but the Lich King’s voice really seals the deal for me at least that he’s Arthas and this is a time hijinks plot.
What happens when you give back his memorys? Does the runecarver tell something then?
For example, the memory of Eonar
The only memory I gave him didn’t give me anything to work with. I don’t know about his other memories.
It most certainly does not resemble frostmourne.That aside the lich king (at least bolvar) could see into the realms of death (as said in the intro to the 50-60 experience). So Arthas and nerzhul could probably do that too, then there is the stuff about Nerubians being connected to the shadowlands (Idk how many can of worms blizzard will open, but this feels more like a bag of them). and that is somehow the reason he got the architechtural stuff from the nerubians or whatever.
Runes and runeblades are to my knowledge NOT limited in the shadowlands to the primus alone, there are other places which uses runes etc. Anyway that is beside the point.
The only connection that i could possibly see is the “puppet dancing on strings” but… Too be honest, the primus is meant to be this guy that is the puppet masters in that context, so I just see that as further indication that he is an apprentice of the primus, rather than him being the primus.
Maybe he didn’t use Maldraxxus runes for them.
Yeah it would be SO weird if the planet we spend all our time on is the most important one in the universe…
That’s so dumb. “The spider people have spider-looking architecture NOT because they’re spider people, but because they looked into another reality and liked the spider-architecture from that place!”
read it on wowpedia. It makes no sense at all, but it is from an interview in french, the same interview with danuser where he implies that “The primus teachings could have spread to inhabitants of other realms of the shadowlands”.