The noble lords outside the capital are a more interesting case.
Carissa won't meet them - at least not by accident at court - but in some ways they hold far more power than the factions of the "nobility" that hold reign here in the capital. They may be approximately all under loyalty compulsions to Empire and Emperor, thanks to the Hall of Learning, but there's a reason why Altarrin pushed so hard to keep it in that order, even though there are apparently very strong underlying incentives that nudge it back toward the reverse anytime he's gone for any length of time. He knows well enough by direct experience how far you can push "loyalty to the Empire", if you keep in mind that your superiors are being complete idiots. Not far enough to assassinate the Emperor, of course -
(You can still get pretty far by delegating, if you're skilled enough at avoiding thinking about things. But no matter how clever someone is, training the skill of 'carefully avoiding thinking about the results of your actions, so that you can slip things past your compulsions' is in tension with other relevant strategic skills, like 'understanding how the world works' or 'updating from your mistakes'. People do get frustratingly good at this strategically-not-thinking skill, and it leads to endless headaches in court politics, but...not more than that. If you're running an internal delusion on the premise that you'll be able to prove a subordinate or rival's incompetence to the Emperor alongside proving his disloyalty, you have to actually believe that they're incompetent. It's possible to lie to yourself skillfully enough to assassinate people, this way, but the rate of people assassinating the Emperor that way is...well. Low enough to be acceptable. In Altarrin's experience, there's a cost-benefit tradeoff in terms of precautions and paranoia, there, and it's not really worth the cost of getting it down all the way to zero.)
- but, anyway, if you're a Duke or Baron in a remote landholding, and you last saw the Emperor face to face when you were sixteen years old, you can still get far enough, without any subterfuge at all, just by holding up your required loyalty to the Empire against the fact that the Emperor's most recent orders seem clearly misguided, and must be the result of some politically-motivated officer trying to slip it past his desk.
(And, as best as Altarrin can tell right now, most of those Dukes and Barons do have a genuine abiding loyalty to the Empire. Or at least to its canal-Gate networks and magically-maintained weather, which is hard to disentangle, but - at least until someone starts trying to murder their family members - it's generally not the case that they would rather be anywhere else.)
And they have the land, that bears crops year after year, or provides mineable metals to an ever-hungry Empire. They have their people, and - especially further out in the reaches of the Empire - most of those people aren't going to be under any compulsions from higher-ups. (Of course, basically every noble house, even the most minor rural ones, has at least one compulsioned spy, but you have to assume that they aren't stupid, and can easily work around this.)
Sometimes they form alliances between multiple landholdings. Which are a common source of rebellion, obviously, but doomed rebellions. A team of elite military mages can defeat almost arbitrary numbers of un-Gifted men, plus or minus a few less-skilled mages – and the Emperor doesn't even just have control of the army and its elite mages, he also has bigger arbitrary numbers of men.
The ones who don't rebel are more interesting. In Altarrin's opinion, their local alliances are a lot of what keeps holding the Empire together, at this point. In ways that can be an ongoing headache to him, but still.