The author of the query featured just below this post would like feedback on this new version:
One of Khatsz's closest henchmen sees in Mir a tool to further their own treacherous agenda. [Is "their" referring to the henchman with a plural pronoun, or is it referring to the Khatsz army? Technically, it would refer to Mir, the most recently mentioned character.] Masquerading as one of these beings, they help him rescue a fellow dancer, evade capture, and survive attacks. [I know it's no crime to use plural pronouns in place of singular nouns these days, but it's making this confusing. "They help him" means the henchman helps Mir (him instead of them), but why does one henchman get a plural pronoun (they instead of him) while one spell Dancer gets a singular pronoun (him instead of them)? It could just as easily be "he helps them" or "they help them." Does this henchman have a name? "Bob helps Mir" would be clearer.] [Also, I don't like "these beings" when no beings were mentioned in the previous sentence. Maybe end the first paragraph with: "But Khatsz's closest henchman, impersonating one of these supernatural beings, infiltrates Mir's troupe in order to further their/his/her/its own treacherous agenda." That pretty much eliminates the second paragraph.]
Then betrayals within the army [which army?] put Mir and the other dancers on the front line. And inadvertently reveal how close to Khatsz the henchman is. Mir is severely injured protecting his fellows, kept alive but held powerless by the henchman. Playing along with this traitor may be the army's only chance to defeat Khatsz--or lead to [could make] Mir himself complicit in their defeat.
[Ending with Mir facing the crucial decision: should he play along with Bob the traitor or risk losing the war? is good, but being alive but powerless is not. I'd remove the middle sentence of that paragraph, and replace it with something like: "Mir realizes he can't trust Bob, but wonders: can he use him?"
If all this leaves your plot summary feeling a bit short, add a few more details, maybe about spell dancing.
I don't know how far into the book this summary goes. If the book covers an entire war, this query seems like it's covering just the first few chapters, which might be problematic.