In a monochrome world, nine-year-old Daniel accepts a strange gift: an Emerald, rich with colour. A gift that turns his father mad, causes his mother to flee, and leaves him in the care of a distant acquaintance, stripped of his family and home. Seventeen years later, he returns to his hometown to investigate the origins of the Emerald behind his family’s misfortune.

i dont really understand why he is investigating this. you open with some things that happen a decade ago, but dont focus on what has happened now to lead daniel back to this mystery. if this emerald is cursed, and somehow he escaped it before since he's alive, why is he choosing to go back into trouble? what has happened in his life that this makes sense?

With him, he brings Arthur: a snarky tutee of his who teases him with sharp words and rouses his desire with a piercing gaze. Years of bottled-down urges resurface and threaten to demolish the life Daniel built for himself, if he’s unable to bury them once again.

i suggest looking at some other romance querys to see how they are structured. If this is really a Fantasy Romance, you need to show off a lot more romance. right now Arthur has one sentence dedicated to him. you have their attraction but why is arthur here? what are his goals? why does he like daniel? what does he want out of coming back to a haunted past?

In search for answers, they make a contract with an eldritch being. Their souls bound together; their bodies connected by a magical chain; their afterlives owed to Our Lady in Chains. Only beings of great power can break such an enchantment. But for the boys to attract one, they must get their hands on objects of colour, face their effects, and overcome the monsters they create. Should they fail, they fall into the Lady’s hands for eternity; but then again, if they don’t risk it, they’re hers all the same.

this kinda all comes out of nowhere. you have set up an investigation mystery about a cursed emerald and then "yadda yadda yadda" your way to eldritch pacts. "in search for answers" is about a vague as you can be. they fall into a pit and are suddenly cursed. why should i care? you were setting up an investigation into family misfortune, that seemed interesting, but that is all dropped for eldritch pacts. why does this follow that? what connects these two disparate premises? what events transpire that lead from one to the other?

how far into the book are they cursed? it seems like the real plot of the book is finding the other colorful objects to break the curse. if so, being cursed is the inciting incident, should be established earlier, and you should go into the plot of how they are going about finding these objects to break their curse. "they break the curse or die" isn't really stakes. "arthur discovered the location of a colorful object in the basement of the prime minister and now they must break into 10 downing or remain cursed forever." is stakes. you want an actionable, visualizable goal in front of them.

hope this helps!

This is more evocative than informative. I'd try a version that skewed toward the latter. Like, I don't know if an Emerald is the same as an emerald. I don't know if the world is literally monochromatic . I don't know how the Gem in question did all taht. I don't know why Daniel suddenly after 17 years wants to investigate. I don't know how they make a contract with an eldrich being, or if being in her hands is a good thing or a bad one.

Also, this is just me, I can only apologize, but I was 92% sure that this was Women Writing Gay Men when I saw 'rouses his desire with a piercing gaze.' I was wrong! Still, I might lean a bit more into male desire. The Ladies of Publishing love that stuff. Not too much, not his passion was roused by twinks with calloused knees, but a little more visceral than a gaze. Maybe?