The morning was rank with the smell of blood and smoke. The Valdians had come at dawn sowing death among the Duke’s ranks. Captain Caleena Jerah surveyed the ravaged camp, the sound of clashing blades still echoing in her head.
Priests ran to and fro tending to the heavily injured and giving the gift of mercy to those whose wounds were beyond healing. Caleena clenched the grip of her sword. Her men had fallen like wheat before the sickle. But the biggest slight to her name was that she failed to protect her liege lord.
The young Duke screamed again as Father Gernod applied layers of balm on the man’s shoulder. Green pustules skirted the wound like malignant patches of lichen. Caleena tried not to avert her gaze, lest the other soldiers took it for a sign of

Also adding to the impartial tone I experienced was a lack of why this slaughter take place. Lots of other points for the reader to attach to could easily be crammed into the first thirteen.

Conversely, a lost battle and dire consequences seems like a reasonable start point, tho of course that will depend on the rest of the story.

That is a much more effective opening for me than "The morning was rank with the smell of blood and smoke." Not many readers could even begin to imagine that smell, anyway, so the line feels dead, generic. Your later lines are more alive because it's about a real person who is facing a real conflict.

I don't need to know much about your society to understand that she is not only facing the agony of losing men, but also facing the consequences of failing. This is a person I want to follow into a story.

If I were you, I would focus less on bringing the scene to life through the senses. "Showing" all of the gruesome details of what was an awesome, epic battle is a little pointless to me, when I don't know what was at stake, what they were fighting for, or why I should care. All I care about is the story of Captain Caleena Jerah, and figuring out what the consequences will be if the Duke dies.

I would suggest focusing on Caleena, because she's your anchor for this opening. I don't care about who's fighting who or why or how yet. I'm just interested in her. I'll care about the bigger stuff later. Hook me first, teach me later.

If your focus is her, then build a foundation to her character quickly so that readers immediately begin forming expectations and wants for her. Little things like, "Caleena tried not to avert her gaze" feels weak, especially for a captain. "Caleena wouldn't avert her gaze" is more assertive, more character-defining.