It would make sense, in the way of explaining why The Maw is inescapable except by First One's methods. Only that door can override Zovaal's command because is a failsafe.
Also, the more I think about all of it, the more fishy all looks:
* Zovaal goes rogue and is punished.
- Doesn't seem weird that the less warrior-like one of the 5 is the one taking action?
- Why none of the other even know about what Zovaal try to fight?
- Why the Prelate, being the best strategist in the universe, know nothing about it?
* The Primus then creates uses domination magic to imprison Zovaal in The Maw. I could get that if they kill him, Zereth Mortis just creates a new copy, but...
- Why domination magic seems terribly close to Automa language?
- Why the Primus looks like he does not know how it works? A kind of magic that allegedly he created?
* The Primus hides his sigil and goes to visit Zovaal. He creates a series of tests in case he goes missing.
- Why did he go in the first place?
- Why did he was suspicious to the point of hiding his sigil?
* Zovaal somehow gets free and uses domination magic to imprison the Primus.
- Why neither of them explain how?
- How the best strategist in the universe is caught by surprise by his prisoner, with his very own magic?
* SL happens, we go to ZM, but the Primus says the EO are prohibited from doing it. Let's asume for a moment that it's true.
- If Zovaal never was there before (and him going to Korthia to get the info about it, to then try to chain Zereth Mortis to his Sanctum), what he did in the first place that granted him eternal imprisonment?
- Isn't Zovaal going there enough to override that command to stop him?
My take?
- Zovaal tried to go there in the first place and they stopped him.
- Then, the Primus knew about the problem and stated to make a plan.
- He sugested to create Oribos and a new Arbiter to replace Torghast and Zovaal.
- He secretly went to ZM and learned about the FO language, and created domination magic based on it.
- He used it on Zovaal to make him his puppet.
- He then puts all things in motion, making Denathrius think that Zovaal is the one with the plan.
- He then goes to Torghast and switches places with Zovaal to redirect possible suspicions, and he sends him in his path.
- When we arrive, we follow exactly what he planed to unite all Shadowland realms, defeat Denathrius, get him free and enable Zovaal to finish his plan.
- He then offers a solution to counter the magic he himself created so we defeat Zovaal.
- Everything is fixed.