I like the set-up here, but I found it didn’t flow easily. I think there is mainly one reason for this: there are instances when the most important topic/element of a sentence is not given top billing within the sentence structure. The top billing in a sentence is, generally speaking, the grammatical subject and predicate. If the main focus of the sentence is clear, it will be easier for us readers to follow the story.
~ Two dark slashes represented the path along which he had been brought to their camp, following a creek’s narrow passage between rock cliffs. In my opinion, “Two dark slashes” probably shouldn’t be so prominently placed. Marc Frederick or the “creek’s narrow passage between rock cliffs” seem (to me at least) to be more important focuses.
~ “The man who spoke, the Kheld chieftain Kadlec Gaal, eyed him suspiciously.” I don’t know for sure, but the chieftain’s name/rank seem to call out for top billing here instead of the man. My grammar isn’t as great as I’d like yet; I’m not sure how to diagram this sentence.
~ “…torchlight glinting off the gold disks fixed to his breast plate.” Within this clause, I think the gold disks are the focus, so I would make them the subject, for example (the gold disks fixed to his breast plate glinting in the torchlight).
~ “…about which he and the rebel leaders sat.” The information he is with rebel leaders seems to important to be in a clause. This topic doesn’t easily mesh with Marc Frederick drawing; I’d consider putting it in a different sentence.
~ “…the path along which he had been brought to their camp…” In this case, I think this topic is too important to be placed in the middle of a sentence with a different main focus (describing the location of a possible place of battle/defence). Its placement there also dilutes our focus from the main focus of the sentence.

“He picked up a piece of charred wood and drew three big circles on the surface of the flat stone about which he and the rebel leaders sat. “The king’s soldiers are here and here. You are here.”” It took me a little while to realize the circles represented the king’s soldiers (I’m embarrassed to say it wasn’t until after 3-4 readings). If the dialogue was right next to the description of the drawing, I think the relationship would be more clear.

My impression is that “slashes” and “mouth” aren’t the most accurate words in their contexts, and therefore not the most clear.

“He himself possessed no weapon but his tongue and, although this wasn’t the first time he’d pitted it against drawn swords, he prayed it wouldn’t be the last.” I think this sentence is somewhat unclear because of the triple negatives.

I’m sorry this was so long, but I wanted to be clear. : ) Hope it is helpful.

All that said, I still was intrigued by the story, and would want to read on.

Holding a defile for a month didn’t seem plausible under any circumstances. Proper fortifications, yes, but no natural site is likely to be that defensible.

I’d read on to find out more about the setting, and why Marc frederick is where he is, doing what he is. But I think I need some assurance he’s more than just a typical lives-by-his-wits fantasy rogue. At the moment, the characterisation is all of Kadlec Gaal.

Overall, I think it’s very good. There’s only one point I’ll make - your pacing needs some work; by the end, I was champing at the bit to try and get past your narrative. I was completely hooked up until ‘You are here’. Then comes the next sentence, and it’s a bit overly long for my liking, but ok never mind things are getting back on track again. Then new character, good, still interested, then HUGE description of the world and his wife, then back to the matter at hand. Yes you need to give us some information about Kadlec Gaal since clearly he’s an important character at this moment, but I think ‘Short and broad-faced, Gaal sat on the other side of the stone table, torchlight glinting off the gold disks fixed to his breast plate’ is quite enough for now. The other details - i.e. everything from ‘each disk…’ to ‘…wouldn’t be the last’ - can come later.

Other than that, I’d most definitely turn the page.