The character description in this logline jumps out and not in a good way. Currently there are three things the MC is: young, a candle maker and has magic powers. Economy in words adds power to a log line so better to use a shorter more potent description for the MC preferably a description that will make it seam like the MC will have a hard time achieving her goal.

The ally being aloof reads more like a Don Quixote type character than a monster fighting hero, what will be his function in the story once they enter the dark realm? Also what is a dragon night? Is he a dragon or a night that fights dragons?
Perhaps better to describe him in a way that clarifies his use to the MC.

Lastly there appears to be two separate parts to the story in the one log line; first is about the MC fighting monsters in the dark realm the second about saving her brother.

I understand that the second part of the logline is there to put pressure on the first but it doesn’t read this way. For the causality between the two parts of the log line to be clear define the inciting incident as the kidnap of the brother by the sorcerer first then describe her action in fighting to save him.

example:
After an evil sorcerer kidnaps her brother a young candle maker hires a retired dragon slayer to help her rescue her brother and save the land from the sorcerer.

Hope this helps.

I think this would work better in a more tangibly real and familiar setting of a known war as appose to a scifi adventure in a non-real world.

The whole story is an analogy to the question; does the end justify the means. A sergeant once asked me if I would follow every command he gave me I said yes, he then asked if I would shoot a child at his command and I said no, he just replied think about it and I did. Later in my service I made a choice that to this very day I don’t know if I should be proud or ashamed of.

The point is that if you are able to establish beyond doubt that both soldiers are the most dutiful and loyal soldiers in the platoon and therefor chosen to cary out this secret mission. Then infuse into the readers mind the idea that one of the two solders has reasonable doubt that the captured man is a good guy this would be enough to create stakes for him. Pin these stakes up agains a their sense of duty and you have a great dilemma.

The external goal would be to extract the target where as the inner goal would be to over come duty for sensibility and humanity. The internal goal could then inform the outer journey and change it to save the target instead of deliver him to the commanders.

my quick little try;
After a special forces soldier realises his captive target could be innocent he must fight his partner whilst trapped behind enemy lines to prevent them completing their mission.

Hope this helps.