Well, that's a thing to bring up.

"Possibly you can," he says. Reducing the odds of insanity as opposed to other possibilities is certainly useful. "I do not think that allowing you to lay compulsions is a useful program under the present circumstances," and fraud!Dalan knows this and mad!Dalan probably does too, accurate!Dalan might not, but it's a very obvious fraud to bring up. "Writing a number of spells you could not plausibly know would be a useful way to eliminate a number of the possibilities, I think." Specifically the ones where he is neither lying through compulsions, nor telling the truth. Janos has full Imperial Adept training, and that's something he can check.

Nod. "Will you find it more convincing if you give me a list of spells that would normally only be taught to highly trained Adepts in sensitive positions? ...I might not always know the exact versions currently in use, but I will probably know a version for at least eight in ten of them." Or be able to reconstruct a workable spell on the spot, at least, his procedural memory and intuitions for magic are one of the areas of his mind he trusts the most right now. And it sounds pleasantly soothing to focus on magical theory for a while right now.

"I would find it most convincing if you reconstructed them without being told which ones I already know." If this is an elaborate plot by the kid to get several hours in the governor's mansion alone to write it has just succeeded.

Well, he certainly wouldn't have come all this way just for an opportunity to sit alone and write in a random Imperial official's mansion, and in fact would enormously prefer to be almost anywhere else. BUT, given that this is where he is, several hours alone to think while writing out notation is definitely a bonus. 

Without a list to go on, Leareth is going to be guessing wildly at which spells are at what secrecy level. ...Which, he realizes a few minutes in, might be part of the Adept's intention, possibly not on a conscious level - his compulsions to serve the Emperor might have objections to scheming to learn spells he's not cleared for - but the fact that he's presumably still unsure if Leareth is insane or lying will buy him some wiggle room to pick a protocol that would advantage him if Leareth isn't lying. 

He'll write down the scrying-spell variant that can target a known artifact signature rather than just a location - that might not be that secret, but it's certainly advanced. He can write down a different scrying-spell variant that gets around (what he thinks is still) the standard anti-scrying shield technique used in the Empire, that one must be fairly secret. He writes down a variant of the communication-spell that he thinks was at one point used only in the Emperor's guard. He writes down the specifications for a passive ward setup that detects whether someone passing through a doorway is under compulsions; it's not that sensitive to which compulsions, there's a limit to how much intelligence you can build into a set-spell even with an elaborate focus, but it would alarm if someone's compulsions had been cut. Leareth actually has no idea if that one is either still in use or particularly secret, but it's certainly obscure and complicated.  

Oh, and he remembers enough pieces of how the authorization-key system works on canal-Gates to reconstruct the specs for that, too. He could probably write down the full design, he's done a lot of work with permanent Gates and everything fits together intuitively to him, but that would take, like, six hours, and bigger sheets of paper. 

- after some consideration, he doesn't include the technique for shields that block Gating into, for example, the Emperor's suite. He's not actually sure if anyone alive in the Empire would still remember how to cast those - he has some vague recollection that a lot was lost in some turbulent historical periods after he left - but if they do, then it's probably known to about five people, and it might well count as treason for anyone other than those five people to know it. He's - not ruling out that wedging this particular Imperial official into treason-by-knowing-the-wrong-secret might end up being a way to accomplish his goals here, but he would rather not do it by accident. 

Just that much is going to take him at least three hours. Does the Adept actually leave him to it for that long? 

(If anyone is watching him, or scrying from another room, he looks very focused and actually a lot calmer than before. He's getting thirstier and increasingly in need of using the privy, but if left alone he plans to ignore that until he's done.) 

The official in question will have him escorted back to his room, provided with pen and ink and paper, and, yes, will then give him three hours. (Three hours of being quietly spied on, obviously, but still three hours.) There's watered wine if he needs it and a privy down the hall, though he'll have to have an escort for that, but if he doesn't ask they won't bother.

And then - 

"I find myself oddly confident he'll have written ten classified spells when I check in on him."

"Impossible. You already have checked up on him."

"Not much.

- He doesn't act like a child. It's not easy to explain by a clever trick... that I've thought of."

"... Such as?"

"Say he doesn't speak Jakonan and is repeating the phonetic pronunciation of every word his handler feeds him. His handler needs to be communicating with him in a way I can't detect, but that's not hard, I'm not a Thoughtsenser." And the Empire is short on them. "But then he'd move like a foreign child, and he doesn't. He's careful."

He nods.

"Even if we only assume he has a way to undetectably de-compulsion himself, this doesn't justify him knowing a wide variety of secret spells. By this point we are proposing both that he has some way of superceding all of our compulsions that we never noticed, and that he has access to vast troves of hidden magic - and the magic could justify the compulsion-beating, but not the other way around, and there aren't any foreigners with that level of magic, which means that if he's lying by that theory that requires either means an imperial plot, for what reason we have not the faintest notion, or some mystery force just as implausible as an immortal who helped found the Empire."

"You really just want to meet someone who knew Arvad, don't you."

"Just is an overstatement."

"Because of the sheer scientific value of having an immortal?"

"Scientific, historical - we may be able to make the Emperor immortal if the Empire can rediscover it -" (even if he doesn't want to) "- and what we can learn from him, if he remembers the past. The Empire isn't what it used to be, and if he can help rebuild it... I need to take the chance. It won't work, but I need to take it anyway."

"I understand." And at the next coded hint he's going to have to have a very careful conversation with an off-the-books mage he knows, because he and Janos both know what their priority compulsions are.

It's actually hard to think of ten distinct classified spells on the spot. And Leareth's hand is cramping badly; apparently Dalan spent less time writing than he's used to. He ends up padding the number by adding a few more obscure variants on the scrying-wards and communication-spell, which lets him reference blocks of earlier notation rather than write everything out again from scratch. 

(The side advantage of working on this is that trying to remember magic as it was used in the Empire does eventually prompt some other memories to the surface. They're not incredibly in order, but he can probably say some coherent things about Arvad's life and work. And there's no reason to expect the things he happens to be able to call to memory to be the same as what's written down in the most popular histories; if he's lucky, some of it will be verifiable by an Imperial official with connections in the capital, but definitely not something a thirteen-year-old could plausibly have learned via a provincial baron's library.) 

By the time he's finished, Leareth is very thirsty and badly has to use the privy. He gets up and knocks on the door of them room they left him in; presumably someone is guarding it, and probably he's being scried as well? 

There is indeed someone guarding it! And he is absolutely being scried, though if he's not currently using an anti-scrying spell it may be difficult for him to be confident of that.

Leareth is absolutely not using an anti-scrying spell right now! He hasn't even checked if the compulsions would let him, since the main blocker is that it would take about three times as much power as he can easily channel right now. (He hates the period of time he has to spend with a partially-awakened Gift. It's additionally distressing to be a prisoner under compulsions, of course, but honestly he would be pretty miserable about it even if he had successfully left and were traveling on his own right now.) 

Anyway, all he wants to do is get someone's attention so he can tell them to tell the Imperial official that he's finished writing things down. ....And ask if he could use the privy. 

Of course he can. The privy is available, and they will even leave him alone in it, since observing him with their eyes isn't necessary.

Being probably-scried while in the privy doesn't even register as a concern for Leareth, next to all the things actually bothering him about being a prisoner. He will do his business efficiently, and then...probably the Imperial official is going to want to actually read and check his spell-notation or something? He'll follow the guard's lead for where he's supposed to be and what he's supposed to be doing next. 

Janos is looking over Dalan's notes, and - 

"... Well."

" - Sorry, I don't have a sane explanation either." He hasn't been reading the notes, he's been keeping an eye out for assassins, which is his job, but Janos has been bouncing enough to him to follow a good deal of it.