Many of the important people can shield him out. The ones who can't are thinking about negotiating some kind of agreement that'll break the stalemate and let them take the city.

The church of Sarenrae has summoned allies doing scouting for them (they look like cats); the church of Norgorber has magic weapons; half a dozen people in the Nethys camp are wizards, though only a couple of them even as powerful as he is. The church of Calistria doesn't seem to have much magic stuff right now. 

He heads back before the spell runs out, though he does push it a little into his minute of slow descent, he has Feather Fall. He writes down everything he observed, while it's fresh, and then checks back at the administrative building to ask if Onaku would like a report now or later. 

She will see him now!

He relays everything. " would like to go in for longer in order to overhear more, but I will need a better method than invisibility, my spell does not last long enough. I also have a spell that would let me impersonate a specific low-level soldier, and I could take their place without it being remarked and learn more that way. It would not be very risky since I still have an invisibility spell left today and could simply disappear on them if I were caught." 

"How very useful. I think we'd benefit from knowing more, if we want to drive them off."

"Then I will do that. Expect me to be gone most of the day."

He takes all his magic items with him. It's some risk, but he decides he'll start with Norgorber's camp, since they don't have wizards who might be paranoid enough to cast Detect Magic at random sometimes.

He creeps out of the city, choice of path aided by his quick glance at their placement. Mostly he doesn't use magic at all, for this part; just using Detect Thoughts is enough to avoid passing near anyone who might see him. He finds somewhere to hide, and listens for sentry-minds coming close enough that he can make this next part work. 

And after not too long, sure enough, there are sentries, thinking about how they'd better break the siege with force because they're not going to starve them out if they've found some way to get supplies shipped in...

He really doesn't feel like burning a Suggestion on this part, but - if he's clever he should be able to coax one of them his way with just cantrips.

He selects someone passing closest to him. Reads the particular sentry's mind very closely, since he's going to be trying to imitate them for a while, he's hoping he can mostly play stupid, maybe pretend he was in the sun too long, but he needs to at least know their name, who they report to, any relevant relationships (mostly so he can avoid the other parties). 

Carefully - Ghost Sound to imitate a shuffling sound, a footfall that might be human or might not - Prestidigitation to lift some sand into the air, just enough to look like movement out of the corner of someone's eye... And he waits, crouched behind his rock. 

The sentry notices! He's suspicious. He says something to one of the others, heads over to check it out.

Aroden provides some more sand-scuffing-sounds to get the sentry to walk around his rock, times it carefully, and casts Sleep. 

The man collapses on the ground.

Aroden catches him and pulls him into the shadow behind the rock. He's unsure if the man will stay asleep for long, if at all, once the spell duration is over (in a matter of minutes), so the first thing he does is take out the rope he brought and quickly tie the man's hands and feet, gently to avoid disrupting the spell and waking him, and gag him with a bit of cloth.

He doesn't have long, before the sentry's colleagues will notice his absence and check what he's up to, but - their minds are in range, he can check if they're impatient or suspecting anything yet, or in a position where they'll see him if he tries to carry the sleeping man from the spot behind the rock (decent cover but close enough to the camp that someone might still find him there, before Aroden has time to do much useful spying) to a more hidden place further back. He doesn't want to use his remaining Invisibility spell; he'll need it if he's noticed, to fly out without revealing exactly where he's going. 

"Was there anything there?" one of the colleagues calls after a minute.

Ghost Sound doesn't let him imitate human voices, at least not comprehensibly. He can make some incidental sound with it though, wind and rustling sand, in case his imitation of the guard's voice isn't convincing enough yet. (He was paying a lot of attention to the man's voice and thinks he can get it closer with some muttered practice under his breath, but he hasn't done that yet.) 

"No, nothing," he calls back, a bit muffled. "Must've been an animal."

This means he doesn't really have time to hide the sentry better, though, so he drapes the man into the slight hollow behind the rock, makes sure he's well tied enough that he's not going to succeed at much movement, spills some sand over him, and then casts Disguise Self. He's not quite as well-practiced with illusions as with enchantments, but he can get it very close. If the nearby sentry wants to come closer than five yards, or have an extended exchange, his plan is to cast Charm Person and use that to cheat at convincingness, probably most wizards can't use Charm Person that way but he can do it with a lot of nuance.

He tromps back over to the stretch that the man had been covering, and imitates his previous movements. 

"Dawnflower's got animals," the man calls back; he's thinking of the summoned cats the church of Sarenrae uses for spying.

That takes him a moment to parse but he's able to answer with a barely-noticeable pause, sounding as much like the other sentry as he can. "Well, I don't see anything now," he calls back.

The other man doesn't argue.

He paces the route belonging to the man he's impersonating for a while. Reads thoughts. He has exactly an hour and should figure out if he's close enough to camp to read everyone's thoughts or if he needs to figure out some excuse to move. 

...He keeps the corner of his mental eye on the sentry he knocked out with the sleep-spell, circling back to check if there's anything in his surface thoughts, he wants some warning if the man wriggles free of his bindings and sounds the alert. 

He wakes up, after a little bit, but doesn't succeed at getting loose and does not try to make a lot of noise, possibly because he is unsure whether that will get him instead stabbed. He is trying to think who among the other allied churches or the rebels could be responsible and whether they're still nearby.

Well, that's something. 

Can he read any of the important decision-making people from here, or at least people who seem to know things about what's being planned? 

He is too far from the central buildings to get a read off anyone who isn't a guard or digging a trench.

Can he skim from their thoughts what the usual process would be for asking someone to cover his position to, for example, use the privy - or whether enough attention is being paid that they would notice and intervene if he just walked purposefully somewhere else? 

At first the colleague who noticed "him" go check behind the rocks is glaring a bit suspicious, but he subsides after a few minutes. Some of the guards are walking around without attracting much notice, especially when someone calls out to them from one of the various tents.

He waits a couple more minutes, picks a moment with a convenient peak of distractions and people in conversations or facing the other way - taking special care that the previously-suspicious fellow guard is occupied for the moment - and then heads off toward the central cluster of tents, at a steady but not hurried pace, trying to radiate that he's headed exactly where he's supposed to be.

- and looks for a good place to mostly be unnoticed or at least left alone, he doesn't want to spent the next fifty minutes fending off people giving him work to do.

There are ditches, and latrines, and some farmhouses that have been requisitioned as warehouses for the church.