He hopes that Malak's last bout of ignorant conscience-serving doesn't actually result in millions of people being tortured to death but finds it mildly annoying that Malak considers this obviously worth it on principle.

Malak thinks that inside of a simulation which may be intended to test when one compromises on one's principles is an especially bad situation in which to compromise on one's principles. And that taking hostages from neutral parties seems unlikely to prevent millions of torturous deaths and is definitely not worth it without a solid expectation that it won't lead to exactly the sort of civil war that he's supposedly trying to prevent.

"I will be sure not to give you any opportunities to demonstrate your principles to whoever you think is running this. And the scenario I anticipated was that Lúthien would go to Tol-in-Gaurhoth, get herself captured, and thereby provoke Thingol into a fight he'd certainly lose and certainly attempt anyway. Even if you think you can influence her into not trying that, you must agree it's what she'd have done unprompted?"

"If I believed for a moment that that were your motive then I still wouldn't think it was justified, judging from the letters Celegorm says you've received it seems as though trying to hold her would just provoke Thingol into war with you and I don't think that was non-obvious when you made the decision. And somehow I doubt that your intention in holding Lúthien was to prevent her father from warring with your mutual enemy."

"...Doriath was never ever going to march to war with us. Thingol deliberately attempted to invoke a centuries-old incredibly dangerous magic to force our hand into murdering someone for his convenience, there is no ambiguity about whether he would ever help us. He's threatening to go to war with us right now because we can't prove she's safe. I assure you that I very very much prefer Doriath not run off into a fight with Thauron, because I have seen four and a half bloody centuries of this and they would lose, badly, and the Enemy wouldn't even come out of it any weaker."

"And you're definitely not the sort to write a politely worded letter, 'oh, Thingol, glad to hear from you, we stopped your daughter from chasing her boyfriend to his death, we'll happily return her to Doriath as soon as the area's safe enough for her to travel, unfortunately we have this werewolf problem and she'd just be in too much danger travelling back right now, my conscience couldn't bear it if anything were to happen because we sent her back too soon.' Right."

"Thingol was also holding her prisoner, she didn't want to be handed back over."

"And I find his stance on the matter equally objectionable and completely irrelevant to whether or not it's OK to use her as leverage against him."

Malak rubs their temples.

"This is not productive. I am going to sleep, talk to you tomorrow."

"Sure. Do try to avoid deciding you know everything and lighting it all on fire because it's not real anyway."

"Don't worry, if I decide to end it I'll only light myself on fire."

Malak goes and gets acquainted with a bed.

In the morning breakfast is brought.

Malak eats breakfast, then heads back to Curufin's rooms.  Knock knock.

"Hey! Our team on this made some progress overnight -" and he would be delighted to tell her about it!

They would be delighted to hear about it! And to test illusory music if anyone would care to provide a sample to copy?

He'll sing something! It makes it windy.

Malak will want to hear it a few more times to memorize it exactly, then the sound of Curufin singing is coming from empty air.

Works.

Lovely!

...So, what, exactly, tends to influence how well a magical song works? Does volume make a difference? Tempo? Pitch? What happens if there are three illusions of the same voice singing?  One illusion of three copies of the same voice singing? Two different people singing the same song? Illusions of two different people singing the same song?

...Unfortunately, Malak does not have an eidetic memory and is not particularly musically talented, and they want to scrap the illusion to work on teleportation tomorrow anyways, so they can't just memorize every magical song ever written, but it's still good that they know about this interaction.

More people and more talent both make a difference; volume affects the radius of the effect if it's an area effect; faster tempo makes the effect kick in a little sooner up to a point where it stops working at all; if it's off pitch it doesn't go. 

And how effective are illusions compared to the originals?

Just as good as Curufin, who doesn't specialize in it - "Lúthien'd be better -"

"Yes, she seemed very talented. So are you, by my world's standards. Depending on how quickly I can get teleportation compressed I can probably relearn illusions in the next week or so...

"Speaking of, if I stay here much longer I still think she's likely to run off to Tol-in-Gaurhoth on her own, so I should probably head back north today or early tomorrow. We are probably going to make a rescue attempt soon and while hopefully weapons will make no difference I am sure that not everything will go according to plan. I don't think you or your people have any obligation to help us with this, but you have a supposed interest in preventing her capture and a real strategic interest in preventing my death, and if you find those sufficiently compelling reasons to arm us I will be grateful."

"You're going either way?"

"Yeah. I'm not exactly unarmed even when 'unarmed,' and with invisibility and teleportation I think the chance of success is at least decent and the risk of death or capture is really quite low. Lúthien is at somewhat greater risk but I'm shaping the plan to minimize that and if I didn't go soon she'd go on her own."

"Then by all means take whatever you need."