Meet my Hatchet of Death (or, some other colorful description RC Lewis and I come up with at any given moment). This is how I edit myself, it is how I edit others. If you think you want to play with me and my hatchet, shoot us an email.
We all know the first line of a query is your "hook." I call the last line the "sinker." You want it to punch them in the face, in a nice, friendly kind of way that makes them unable to forget you after having read the 300 other queries in their inbox.
If you're looking for query advice, but are slightly intimidated by my claws, blade, or just my rolling googly-eyes, check out the query critique boards over at AgentQueryConnect. This is where I got my start, with advice from people smarter than me. Don't be afraid to ask for help with the most critical first step of your writing journey - the query. My comments appear in green.
Caetlin Lovelell and her family are shadow slaying tunnel guardians by night and socialites by day. It might be better to explain first what this means, rather than jumping in with a hook that has to be untangled. They protect their patrons is this the right word to use here? of the supposed city of prosperity awkward phrasing - are you saying it's supposedly prosperous, or supposedly a city? The phrasing right now could go either way, and the sentence structure is overly complicated in trying to get to the underground baddies, Dorme, against the shadeu— creatures lurking underground that live off human flesh.
When there is a sudden change in the behavior of the shadeu, don't need this comma and guardians start to go missing—including Caetlin’s own brother, Caetlin and her sisters will do whatever it takes to find their brother and protect their family from the war brewing in the underground tunnels, even if it means allying with a mysterious— and most likely dangerous—vagrant guard to do it. This whole paragraph is one sentence. There are plenty of good stopping points, definitely use them.
I don't think you're getting what makes your plot and characters distinctive and new into this query. What is the sudden change in behavior? What kind of war is brewing in the tunnels? Humans versus shadeu? Hasn't that always been the case? Is it a secret that the socialites are warriors? What is Caetlin's personality like? Her brother? Is the guard a main character that needs to be named? And why would a vagrant be a guard in the first place? Get the individuality of your story into the query.