I honestly think it’s MC and Prestige.
Think about it: he’s been fighting the Dozen for decades. Every time one is arrested/beaten, they are replaced by another. MC must be in his forties, and near retirement (it was mentionned in the WiP that he was grooming Trendsetter to be his successor).
And yet, he isn’t able to beat the Dozen (no one is due to how they work) and Savior has been preparing to make a powerplay for years.
Here’s my theory: Mega Cat is negociating with the Dozen because they are a lesser threat than Savior. When you think about it, the Dozen just want to be criminal overlords and are rather divided (the Manipulator herself said so). What’s the worst they can do? Destroy a city, kill a few thousand people?
Savior on the other hand is much more dangerous. Why? First they are likely more popular due to their so called transparency and the fact they admit more people. In case of a conflict, it’s possible that they will have the public’s support. Second: due to how B***ismart is building her army, they will certainly be fanatically loyal to her. And finally: pure numbers. It doesn’t matter how strong your students are; if your opponent massively outnumbers you (thanks to their admission policies and the creation of new Zeniths) then you are fucked.
So MC prepares a plan: he’s not able to create Zeniths, so he has to tip the scales. How does he do that?
He contributes to the creation of Speck. This solbes two problems: the front isn’t as close to New York as it could be and he has a presence near a zenith weapons arsenal.
The former means that since the battle will occur in the middle of nowhere it’s unlikely that Savior can recruit people during the conflict. Think about it: if they fought in New York, they could recruit people from all over the east coast ensuring a victory by attrition.
The latter means that he can even the odds with the weapons. Moreover, he likely has more political clout than Savior (he was there before, probabbly fought the Dozen more times and NY is closer to Washington). Why is that important? Because while Savior could give the US a Zenith army it’s obvious they would keep a monopoly on it and try a passive takeover of the government (it seems like their main tactic). So in case of a civil war between the schools, MC will likely be backed up by the military. That and the arsenal is probably enough to compensate for their numbers.
But then you’ll ask me: “If MC is negociating with the Dozen and needs Speck, why did he let them attack the city?”
That’s the main flaw in this theory. Did he think that Speck had been taken over by Savior and that he should let the Dozen destroy the school then swoop in like a hero? But then, why let them attack St Louis etc?
My main theory would be that MC and the Dozen both intend to betray the other, which will lead to a three way war between Prestige, Savior and the Dozen.