Originally Posted by
Triceron
Very good. You're asking the right questions.
When was this pact made. Answer - We don't know, and we have no reason to assume when without canonical information to support it. We don't have information to suggest any given timeline. 'True master' is not a hint at any given timeframe, since this would apply whether he was always serving Zovaal since WC1, or if later adopts him as a master after the events of Wrath of the Lich King.
If you are asking for an opinion on your speculation, then I'd say I'd disagree with your speculation since I don't view Ner'zhul as weak, and I view Blizzard actually fucking their own lore by painting him as a weak-ass bitch when he should have remained as the 'Sauron' of the series. Even if he isn't Morgoth, they shouldn't have retconned all his accomplishments away as if he was simply a puppet. I personally think that it should have remained as *his* cunning that deceived the Legion and propped Arthas into the position as the new Lich King. Changing that credit to Zovaal doesn't change Warcraft 3, considering that story is self-contained to talking about the known characters, and not hinting at some future villain that is being retroactively fit into that specific story.
Again, same as Old Gods not directly appearing in the story even though we know that even Yogg had his tendrils in the creation of the Lich King.
So I will say that your speculation is possible, though I will adamantly disagree with it since I don't even agree with Blizzard's current treatment of the lore. I openly criticize it just as I have pointed out how Zovaal literally came from nowhere, and how it was a poor way to implement and introduce this character when they could have planned him YEARS in advance the way they did for N'zoth, Muehzela and many others. And I adamantly disagree with Blizzard's choice to redirect credit away from Ner'zhul and to the Jailer.
I have to question the integrity of your speculation.
What reason do you have to assume Dark Lord must contextually be referring to anyone other than Ner'zhul? I mean at this point we're literally verging on Headcanon because you personally view Ner'zhul to be too weak to ever be referred as a Dark Lord. I can understand the sentiment, but please understand that I have no intention of sharing your sentiment.
I've been in discussions where I've seen people say Arthas was always good, and that it was Frostmourne/Lich King who pushed him to do every bad deed, and that Arthas was 100% innocent during all of Warcraft 3. That is a headcanon viewpoint, because Warcraft 3 shows Arthas choosing a dark path by his own will. Whether Blizzard seeks to retcon that through WoW lore or the Novels is irrelevant to Warcraft 3's own self-contained storyline. So someone headcanoning that it was the Lich King or Zovaal that caused Arthas to do the Culling and not Arthas' own choice would be headcanon, even if it's an attempt to bridge in an 'innocent' Arthas like we've been seeing lately in WoW. The fact is, we won't have an innocent Arthas unless Blizzard retcons the events of Warcraft 3. I have no interest in a Zovaal that controlled Arthas any more than I do of an Arthas that was always good and that he was supernaturally co-erced to make dark choices. Arthas is not Medivh.