Altarrin doesn't watch through the entire time. Scrying a site a hundred miles away, for candlemarks, is draining even for him, and also takes a lot of focus that he needs to apply to other things. He does watch long enough to notice when the winged woman loses her wings, which is interesting and might mean there's a limited duration to the godpossession – though it doesn't look like the lack of wings impairs her very much in efficiently killing huge numbers of people.
(And this is supposedly the god of flourishing civilizations...)
His main priority for right now is giving a full handover of the Taymyrr-related logistics and current state of tactical planning to one of the other top generals of the Empire, because it took Bastran about four seconds to read Governor Vanaren's letter and decide he wanted Altarrin personally on this. Taymyrr might get messy and unpredictable, but Oris is already messy, and 'unpredictable' is a vast understatement of what just happened.
It is, yet again, incredibly frustrating to try to get anything like an accurate post-battle headcount, but his guess is that the rebels took relatively low casualties in this fight. The Adepts were focused almost entirely on the godpossessed Knights of Ozem, and meanwhile the rebels' Adepts - of which there were much fewer, but still - were able to do whatever they wanted. And the Imperial soldiers were taking the morale hit of being in the middle of a losing battle from almost the beginning, even when their compulsions didn't actually let them just run away.
He's going to need a serious numerical advantage, both for the obvious reasons and because he very much needs this to be a fight that the Imperial side is confident they're going to win. This is - doable, barely, but annoying. It's going to mean leaving Isk almost bare and hoping that Vkandis isn't going to lean on Iftel to take the opportunity to invade, or at least that if they do it's going to take them a while to be ready to move.
Most of all he needs Adepts. Who are willing to die. It's a different ask, ordering someone to go into battle knowing from the beginning that their plan is to sacrifice themselves to explode at their enemies.
It looks like the rebels are planning to spend a while consolidating. Which is good. If they pushed hard to chase the remnants of Governor Vanaren's forces and take Havau Bar, it would actually be pretty hard to get reinforcements over in time.
He watches in snippets as the rebels move in to occupy Tatanka.
He's...impressed, honestly. It's a much more disciplined occupation than he would have expected, and - it's hard to tell by scrying from a distance, but he suspects the no-longer-winged woman has a lot to do with it.
Maybe it does mean something, to her, that Aroden claims to be the god of civilization.
He watches, and plans, and weighs the pros and cons of sending another letter to the Knights of Ozem, who may or may not have received the first one yet, though if they haven't it should be reaching them soon.