Quicksilver

Why these tropes fit

Saeris, a thief concealing strange Alchemist powers, is hurled through a gateway into the Fae realm of Yvelia, where she accidentally bonds herself to Kingfisher—a handsome, murky-past Fae warrior who is literally Death. He intends to wield her magic for his people's protection at any cost to her, and since he's her sole route back to her own world, the two are locked together in a forced-proximity clash of agendas that edges toward an enemies-to-lovers arc steeped in fae lore and centuries-long conflict.

Evidence from the source

• Fae Romance: “The Fae have always been the stuff of myth, of legend, of nightmares... but it turns out they're real” source
• Chosen One: “The first of her kind to tread the frozen mountains of Yvelia in over a thousand years” source
• Forced Proximity: “he's the only way Saeris is going to make it home.” source
• High Fantasy: “she inadvertently re-opens a gateway between realms and is transported to a land of ice and snow” source
• Morally Gray: “Death has a name. It is Kingfisher of the Ajun Gate. His past is murky. His attitude stinks.” source
• Fated Mates: “Saeris mistakenly binds herself to Kingfisher, a handsome Fae warrior” source

Metadata source: Open Library. Quotes are used only to verify the tags.