Alright, back at it ;) I think I pulled the query from the topic of the second page instead of the first last time, sorry! I haven't looked at may synopsis entries (just started looking at requirements for this today for my stuff and my head started spinning! haha), so hopefully this isn't unhelpful.
Other note- I've found it frustrating to have holes poked in my query (i.e. a random "too vague" or "why" etc.) without any actual constructive assistance, so in several instances after poking at you (and this is good natured, so hopefully it doesn't come off harsh ;) I've offered a different wording or sentence. Take these with a grain of salt as I've not read you MS so I might be headed way off in the wrong direction from where you're trying to take us without realizing. Also, I clearly have not labored over this as you have, so take the examples as a suggestion, not a shiny A+ piece of writing that I'm suggesting you use as is ;)
Synopsis: (Beginning to end)
Born with the ability to visit the dangerous city of Nasper in an alternate realm, eighteen-year-old Faye Hex believes it is where she will find her parents I'd switch the clauses around here to make it more active, something like- "18yo FH is searching for her parents, but not on Earth. Faye was born with the ability to travel (maybe a more interesting word than "travel" though) to an alternate realm where she searches the dangerous city of Nasper." This gift is tied to the presence of Troy Tucker, another orphan. Only when in close proximity are their souls free to wander the abandoned city. Two things here, first, the word order of this sentence reads funny, but if you reorder as suggested above (but obviously better) it might not be an issue. Also, it threw me a bit to have you describe the city as both "dangerous" and "abandoned" it sends me in the direction of Raiders of the Lost Ark with them getting sabotaged by pillars and such. Since I read your query previously I know you're referring to non-human entities, but if this were the first pass I might not get that. A simple fix would be to insert that it's been abandoned by humans specifically.
However, abandoned does not mean lifeless. After a near-death encounter with a vicious black (see prior note about the banshee being black, without context this might not be the ideal descriptor) banshee, Troy begs her to stop the search for her parents.
Unfortunately, don't like this word, makes the MC seem passive, like things are happening to her instead of her creating the action Faye grows desperate after learning that Nasper is dying. And if the city dies, so do the clues about her family. "After a near death encounter with a banshee Troy puts his foot down. But when they learn that Nasper is dying Faye becomes even more desperate to find her parents before the city, and her clues, are lost forever."
Troy puts distance between them to contain Faye’s recklessness. Again, this sounds a bit passive. "Troy refuses to see Faye, hoping distance and her inability to travel without him will contain Faye's recklessness." Unable to connect with Nasper, locating her best friend becomes priority. "Frustrated, Faye turns her attention to finding Troy, but when she does it's already too late." But, it is too late. Troy returns this throws me a bit because it suggests Troy went to Nasper without Faye, which 1. I thought was impossible, and 2. he's the one that didn't want to go in the first place., and not as himself. He died and was revived by Nasper as a white banshee with the power to dissolve into billions of particles. Confident so is this a good thing or a bad thing? "too late" suggests bad, but "confident in his new ability" suggests good in his new ability, the couple So you've referred to them as friends, best friends, and a couple. I'm unclear of the relationship between your MCs at this point. explores the city again. All clues lead to the discovery of two malevolent leaders who control the black banshees Okay, so I see now that "black" is not so much a descriptor of an individual banshee as it is a whole group. I'm of course familiar with the ideas of "white magic v//s black magic" but the "black is bad and white is good" thing might be itchy for some agents, especially with current events. Again, I'm no expert, it just stood out to me.. With their desire to kill all who have access to Nasper, Faye realizes that her parents have been in hiding all these years. This isn't a super jazzy ending for me. I feel like the stakes have gone from "Faye's parents are trapped in a dying world and MC have to save them and the city from the evil banshees" to "oh, well I guess they're hiding and couldn't be bothered to take their child with them." I don't have a specific comp here, but maybe knowing why Faye's parents have been in hiding, and having it be more dire than them knowing about Nasper, could up the ante a bit.
Summary (2/3rds of the book) ends in:
Troy puts distance between them to contain Faye’s recklessness. Unable to connect with Nasper, locating her best friend becomes priority. But, it is too late. Troy returns and not as himself. The city has changed him. What she witnesses may force her to choose between each other I'm not sure who the "each other" is referring to, if it's Troy just use his name since we're familiar with him and Nasper.
Like I said, I haven't really taken the dive into synopsis-world yet, so I hope this is more helpful than frustrating!