"I'm assuming you do that all the time anyway. Am I wrong?"

"No."

"I just came out of a very ugly war zone. I would rather avoid personally killing anyone because supposedly doing so lowers some inhibitions but I'm not going to be really precious about it. Besides, I'm told they're recoverable."

"Especially if we can erase their oaths. Does your magic system destroy chronic pain, by any chance."

"I was working on that when the war hit, I hadn't quite got it. Unless it has a physical cause like a kidney stone, I can destroy the hell out of kidney stones."

"I don't know the cause. It might be physical." Orcs are created by raising successive generations of Elves in constant torturous pain; subsequently the pain is innate, so all orcs are being tortured all the time. Not in a way that makes them less functional, it's just -there.

"...tricky, if not impossible, but maybe. Should save it for when I have leeway for experiments though."

He nods. 

"I can get underway on designing the spell for oath-busting once I know enough about oaths - any detail could be helpful in avoiding side effects."

"Hmm." You have to swear oaths by speaking aloud. You can swear them to a deity - Vala or Maia - which gives that deity the power to release you - or to a general audience, which means no one does. If you do not specify a time frame an oath is active forever. Ambiguity is resolved by the understanding and intent of the speaker, but a slightly strange understanding of 'intent': if I swear 'I will not lie to you', intending primarily to get you to give me magic instead of to bindingly commit myself to future honesty, I am absolutely bindingly committed to future honesty. I intended to make it understood to you that that was what was happening, and so that is what happens. If you swear in a language you don't know, then the oath will not affect you until you're apprised of its contents and the fact you made it. Same if you swear while barely lucid, which is why torturing people into oaths is only moderately effective, or if you swear as a young child, though I think the Enemy has you repeat it as you get older in order to avoid this problem somewhat.

Cor writes this down in a bulleted list.

You can swear to alter states of mind, with some constraints. Orcs swear to hate Elves and that mostly works; swearing to forget something happened doesn't usually work well; swearing to believe everything someone says has wildly unpredictable results from 'collapses in internal confusion' through 'just finds that person super trustworthy'. If you make an oath that absolutely proscribes a course of action, you'll find you just literally can't take it; your body won't move to complete the steps. If you make an oath that demands a course of action, you merely find it overwhelmingly, distractingly tempting, and gradually you lose the ability to have desires or preferences outside that course of action.

"It is... possible I can't de-oath somebody without making them not an oathgiving creature any more."

...huh. With orcs that's obviously worth it. With Elves... I can probably find a volunteer but I think they'd consider it a genuine sacrifice. We know how to be safe with them and they're useful for credibility.

"I can try but - the way spell specifications work is more 'describing an aesthetic to the magic' than 'issuing complex specific instructions'. The destruction-only part is hard-wired or it'd be very... uh, it's kind of like writing an evocatively descriptive paragraph? You will get a thing that is metaphorically by the same artist of the same subject in the same color palette as what you had in mind, if you know what you're doing, but maybe from a different angle or with a different... paintbrush... I don't know anything about painting, that got away from me... uh, anyway, it makes it hard to leave precise exceptions, if you're weeding a farm you go 'imagine a farm with no weeds', not 'imagine a farm with only that one weed over there' because if you do the second thing the magic might go 'oh you mean those three weeds? we're doing a "some weeds" thing, right?' and - yeah."

Nod. Will it consider marriage to be a weed? Elven marriage is a binding of two souls for all eternity.

"That sounds aesthetically different, more 'leave the flowerboxes alone' than 'protect farmer's daughter's favorite specific dandelion that she named Sunbeam', yeah."

Giggle. Okay. I'll ask around and find you somebody to try it on.

"I can't guarantee the marriage thing, it's just somewhat likelier to survive than poor Sunbeam."

"We'll try someone not married who will not be sad if it happens they can never marry."

"Cool. I can get going on spell design now if there's nothing else I should know about oaths or aesthetically nearby things."

He glances at Curufinwë.

"I'm not sure what else might be relevant. Valar and Maiar and Elves and orcs can all make oaths. The state of having made an oath doesn't feel like anything. If you cannot progress towards achieving something you sworn to do you can pursue other things you care about normally. You can't derive new information by swearing oaths; I couldn't swear to hate traitors and thereby learn which person in a battalion was a traitor, or anything like that."

"When I said any detail might matter I meant it, if I get it wrong by a little I spend a few hours knocked out and if I get it wrong by a lot I start harming the subject and/or losing toes."

Nod. "You make an oath by saying 'I swear'. 'I promise' doesn't do it. It survives death and reembodiment."