A while later a guard tells them that orcs have been brought. 

"Thanks. Is there any reason we shouldn't explain why I am going to paint substances on and around them and chant before I do it?"

"Enemy could be reading their minds."

"...he could also do that during or after the painting and chanting."

"Yes but then all he'd know is that we have a way to break oaths, which involve speech in a foreign language, as opposed to having a full explanation. I suppose there's nothing to be lost by telling the orcs that we're going to free them of their oaths."

"I mean, if I want them to actually deliver letters as opposed to appearing terrified and bewildered in downtown recently-war-torn Gatesnest to be promptly arrested for obstructing traffic, they will need an explanation."

"The letters can't have the explanation?"

"I have never been arrested but I don't think they make a habit of confiscating and reading people's papers, we'd be gambling on someone being curious about their spontaneous presence or what they look like enough to get intrusive. Also, like, the poor orcs, getting kidnapped by Elves is at least in the realm of possibility - I have to assume - but they're going to land in Gatesnest and everything's going to be weird and spacewarpy and human and absolutely no one will know their language."

"I empathize but you should assume anything said in their presence while they are here may as well be said directly to the Enemy."

"...what exactly do orcs actually look like, let me calibrate how alarming they're going to seem."

He sends a mental image.

...sigh. "Okay, I will settle for explaining that they're going to be de-oathed and then, uh, pleading after that to end the cycle of violence and hoping they get the hint when they land among people with whom they have no previously established cycle, and they can wear signs."

"Thank you. Sounds good. I don't expect they'll be violent on arrival."

"Hopefully they will also not destroy their signs or letters."

"Harder to guess." 

The orcs are being held in a stone building. They are restrained and blindfolded. There are two.

"Why the blindfolds, is what I look like a secret too?"

What you draw on them and the floor.

"They're going to feel what I draw on them. I suppose I could add extra stuff in a dummy substance."

"And it'd be harder to guess the whole pattern from that. I assume bits aren't very useful."

"Bits are almost totally useless. The whole spell would be if I hadn't already used it, I painted metaphorical oathlessness with the fanciful use of swirls and it was me enforcing the metaphor, it's a reproducible thing now but it wasn't the previous afternoon."

"Huh. So the first casting requires a mental extension of the metaphor and then after that it's catalogued and just works?" We should be quiet, we're close enough now -

It's sort of like very quickly establishing an artistic convention. What, is the Enemy as good at languages as you?

No one alive is as good at languages as me but they can take the memory and play it over a million times and maybe that amounts to almost the same thing.

Okay. I could try chanting over osanwë? It's not completely out of the question that thinking it works if there's telepathic protocol involved, although it doesn't normally.

Does anything bad happen if it doesn't work?