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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.
Invisible to the naked eye, the Haze flows harmlessly through the air. While it passes through most, there are those it gathers and thickens around who can harness its power—Deviants, the very people the governments of Earth have kept secret for centuries. I'm slightly confused by some of your wording in the hook. When you use the phrase "governments of Earth" it makes it sound like there are other planet governments to take into consideration as well, which judging from the other locations you use in the query, is not the case. I think using "of Earth" might make this sound more SF than it really is, and also... I think without being specifically told otherwise most people go ahead and assume that the location is, in fact, Earth. Also, some of the word choice here leans toward negativity - "harnessing power" is a phrase I usually think of as something a bad person does (might just be me, though) and that combined with the term Deviant (also has negative connotations) leads me into this with, "Oh no, Deviant = Bad" feelings, which might not be what you're going for. Lots of talk here from me already with the hook, but I think it needs pared down.
Eighteen years old and the only thing Cal Espers is good for is his sharp tongue and skills with a bow—little good that does in the tedious battle for social vitality. Still feeling like I don't quite have a grasp on genre here. A bow? Cool, but... I felt tech-y SF coming with government controlled secrets, and now we've got a bow. And I'm unclear what "the battle for social vitality" means. Is this a true battle to keep humankind alive? But when the mutilated monsters appear Again, alongside the "social vitality" phrasing I don't know if the monsters are a part of everyday life now or if this is a big, scary, new thing and ravage the streets of Mobile, Alabama, Cal’s sassy childhood friend, Nia, gets lost in the chaos. Cal risks his life to find her when he encounters one of the otherworldly abominations. His trump card: a stolen bow. Wait - I thought he already had a bow? Is this one special? Who did he steal it from? But it isn’t the arrow that shatters the creature’s invisible shield, it’s Cal’s ability to harness the Haze. Cal is a Deviant. Did Cal know this ahead of time?
The Haze is thickening, releasing more monsters by the second, What is the connection of the Haze to the monsters? I thought the Haze empowered Deviants- Cal is a Deviant and our hero, so... is the Haze a good thing or a bad thing? and the governments of Earth are left with one choice: find and annihilate all Deviants in hopes of dispersing it entirely. The only way Cal and Nia can avoid execution is to banish the Haze around them by completing their design—a goal they are given as Deviants. What does "completing their design" mean?
If they can even figure out what the hell it is.
Monsters appear where the Haze is thickest, and that seems to be wherever Cal and Nia go. Until he can figure out his design, Does this mean like, his purpose / goal? Cal must use his archery to stay alive and protect the one person he cares about. If Nia is also a Deviant why isn't she protecting herself? The governments want his head; the monsters want his blood. He’s never been hesitant to release the string, but he’s no longer shooting for self-satisfaction; now he’s shooting to kill.
Our 84,000-word YA urban fantasy, DEVIANT will appeal to older YA readers of the MORTAL INSTRUMENTS and WOLVES OF MERCY FALLS series as it is told from multiple viewpoints. Nia's narrative voice is reminiscent of Zoey Redbird in the HOUSE OF NIGHT series while Cal's witty, sarcastic voice will resonate with readers of John Green. Thank you for your time and consideration. I think you're right with the urban fantasy genre here, but as I mentioned earlier you need to take references to "Earth" out if there aren't other planets at work within the world-building, because it implies more of an SF slant than there actually is. Also, you've got a lot of comp titles here, too many - it makes it look like your book might be unfocused, or trying to do too many things at once.
There's a lot of clarity needed here - I'm unsure whether the Haze is good or bad. It makes Monsters, yet also gives our hero the ability to get rid of them. Our hero is also under threat of both monsters, and the government and he needs to find out a secret about himself in order to banish his own haze... I think. It looks like theres a lot of world-building involved with your story, and that's fine, but you need to re-read your query as if you were coming to it knowing absolutely nothing about your world and see if your brain isn't filling in gaps that it already knows the answers to, which your reader isn't able to fill.