Then why bother arguing with him? 

Anyways, Bellona isn't going to make herself obvious just yet, instead hanging back to listen and try and get a sense of politics here. 

It seems the man, Chancellor Roderick, is the most senior surviving member of the Chantry, which makes him the top civilian authority. Perhaps unfortunately. He's nervous and in over his head and of the opinion that the position is hopeless and they should retreat before more lives are lost. When Cassandra shows up, he switches to trying to persuade her, calling her 'Seeker'. She stonewalls his pleas, calling him a 'glorified clerk'. Some back-and-forth about the dead Divine, Justinia (who both Cassandra and Leliana served directly, apparently). Then Cassandra brings up that they can close the rifts now, thanks to Lionheart.

This outrages Roderick, who sputters about why they let such a dangerous prisoner loose and calls for her to be chained up and preparations made to send her to Val Royeaux for trial. No one makes a move to do anything about this obviously insane order.

(Watching the argument is a bit surreal. Bellona doesn't loathe her country, but - she's still in the military out of inertia. She agrees with Mustang that Amestris should be a democracy. She agrees with his detractors that it's an insane idea. It's... Odd, looking at one possible way that balance of power could settle.)

(They definitely will need to maintain the thing where they have a mostly clear line of succession if their entire high command is wiped out except for one traitor. There'd still been intense - and literal - fighting over the succession, but it was less... Confused than this. Everyone knew who should rightfully be in command; they just disagreed.)

She stiffens her shoulders, falling into a comfortable - and respectful - parade rest. "You need me, sir," she says. "I was the sole survivor of that explosion - a trial is the appropriate way to determine guilt, but right now I am under guard - as you well see, sir - and willing to work with your people to solve this problem and prevent as many further deaths as I can. I cannot do that from a prison cell."

"You were the one who caused the deaths!"

"I did not, and the breach would have killed me as well if not for prompt and highly skilled medical treatment. You currently have no evidence of my involvement beyond that I was present in the area and fortunately survived. That is still enough for a trial by many laws; it is not enough to presuppose guilt, nor a reason to deny an ally the opportunity to keep both of us alive."

Her reasonable and logical defense does not seem to be getting through to him.

Cassandra takes a different tack. "Enough, Chancellor. The Divine trusted Leliana and I to solve her problems. We are here, solving this problem. If you do not like that, return to Haven. Otherwise, stay out of our way."

     "There will be consequences, Seeker. I warn you."

"There are always consequences. Go." She waves him out of the way.

(Leliana details two soldiers to escort Roderick back to the town.)

"I find your political system confusing," she mutters. Though, honestly, they did just lose a lot of their leadership. Any element of Amestris's leadership after the Promised Day that wasn't 'just keep your head down until the shooting stops' was probably very confusing too, from an outsider's perspective.

"You didn't really show up at the most opportune time."

"Yeah. And with how much of your leadership it sounds like you lost - it is honestly impressive you're holding together this much."

"There's a trick to our success. We were planning something, setting foundations for a new organization, something the Divine would have made public- But it's pure luck we were delayed long enough to still be in the valley when the temple blew."

Nod.

" - How magic works is probably more urgent to surviving the night. But I want to learn more about how politics work here, too. I'm willing to trade you how politics work where I'm from - it won't be immediately useful, but if there's contact between our peoples beyond just 'I figure out how to transport myself back, vanishing into the night' it'll matter, and it might be useful for - hm, comparative sociology. Figuring out where other people have succeeded or failed."

"Of academic interest, if nothing else," she murmurs. "It's a deal."

"And insight into me, too," she says with a laugh.

"Context, at least."

"Explaining me is pretty hard."

"I think that's true of most people, in sufficient detail."

"I'm a bit farther out than normal, though, aren't I?"

"For now."

More sincere smile. "You know... If contact with home's prolonged beyond me just returning... There's some people I think it'd be fun to introduce you to."

"We'll see how things go. For now though, we should plan our next move." She gestures towards the table, where there's a rough map of the area with small rocks marking positions of various forces and known rifts.

"Do we need to close all of the smaller ones before tackling the main one?"

"I suspect not," Solas says. "If the Breach is closed, the rate at which the smaller rifts form should at the least slow, or hopefully stop entirely."

"We should bee line for the main one as best we can, then..." She squints at the map, analyzing it, and asks a few questions about how they're representing things like 'the mountain.'

Leliana can explain the map.

There's really only one road up to the former temple, which is the main problem. It's crowded with demons and their forces are holding the line, but that's about all. News that they can now close rifts and support from Seeker Cassandra might be the morale boost they need to enable a push straight through, but it could get bloody. She's also sent a group of scouts up to find an abandoned mine here, which should connect around and provide a bypass route. But it's a narrow climb, limiting the forces they could send that way, and she hasn't heard back from the scouts.