So Iomedae heads north to sabotage Gates. Before she does, she writes another letter to the Empire, though she's pretty sure at this point that whoever has sent her three Lawful but increasingly unpromising letters about how unwilling the Empire is to engage in peace talks with a representative of a god is not the path to mutual understanding. Probably the path to mutual understanding is surviving a dozen Final Strikes and discrediting that perspective, within the Empire, that this is a problem they can or should solve with force.
Accordingly this letter is more pointed.
The Knights of Ozem represent that Oris is prosperous and on its way to being well-governed and that they anticipate the people of Oris, presuming Oris remains free, will be better off in five years and in twenty than comparable people in Taymyrr. (They acknowledge that Taymyrr, also currently the site of a bloody war, may not strike the Empire as the fairest comparison, but their sense is that wars like the one besetting Taymyrr are not uncommon and not unrepresentative of what Oris would have had to look forward to had they remained an Imperial possession; indeed it looks likely they'd have been a site of routine conflict between the Empire and the Holy Empire of Ithik.)
They are happy to agree with the Empire on some formalization of this prediction and some treaty provision that rests on it, if the Empire is interested.
They observe the Empire to be, as according to its own histories it frequently is, beset by multiple internal civil wars. They regret the loss of life and would under some circumstances contemplate offering to help the Empire end those civil wars more swiftly, and under a wider range of circumstances than that they would offer miraculous healing. That can be discussed as part of peace negotiations should the Empire be willing to engage in those; it is sometimes worth engaging in peace negotiations even if it seems unlikely there is any set of agreements appealing to both sides, especially in a situation like this one where the Empire's geopolitical situation may rapidly change.
The Knights of Ozem have, as the Empire knows, committed to operating for this time only in Oris. Under the present circumstances, were it not for this commitment, the temptation would be fairly extraordinary to send an operative to one of the candidates for Emperor, and ask if he'd contemplate permitting the worship of the Church of Aroden were that church to lead him to triumph in the civil war. They are not doing that. The reason they are not doing that is that they understand that, on the Empire's view of the world, the gods desire only the destruction of the Empire, that they object not to its excesses but to its existence, and that on the Empire's view of the world the gods are incompatible with civilization and a place without them is needed for any hope that civilization might prosper. This perspective is obviously incorrect, to the Knights of Ozem, but they understand that it's possible they are mistaken, and do not wish to act in a manner that would be catastrophic if they were wrong. (It also suggests, whether or not it's correct, that the collateral damage from putting the Empire under existential threat would potentially be ludicrous.) And so the Knights are passing up an opportunity that is very much strategically indicated, because they are not enemies of the Empire, and have no desire to see it destroyed.
In the Empire's view of the world, as the Knights understand it, the gods have created this entire situation in order to destroy the Empire. This might inspire one to wonder: if the Knights are firmly committed to not being used as the instrument of the Empire's destruction, what are the gods steering for? The obvious answer is that the gods are steering for the Empire to foolishly grind itself to exhaustion trying to destroy the Knights in Oris, expending its most valuable resources on battles that it could easily avoid, and thereby weakening Bastran's reign such that he loses one or both of the civil wars.
(In the Knights' own view of the world, the Empire is doing this all by itself and no god-intervention is required to explain it; Aroden trusts His people and is letting them do as they see fit, and His people are trying to assist in the development of a functional, prosperous country that does not run on mind control and executions. But they are not sure they are right - no man ever should be, really - and so they have contemplated the Empire's view of the world and taken action to limit the damage they do, should the Empire be correct.)
The Knights of Ozem entreat the Empire to contemplate peace talks, which would reflect no commitment to a peace but make it possible for common ground, if it exists, to be found.
She'll send it along with copies of all the earlier letters, in case they have been getting lost somewhere.