Demon Seed by Matilda Martel

Just beyond the bustling city of Ravenwood, nestled in the shadow of the Blackthorne Mountains, next to the Forbidden Forest, lies the mysterious village of Nightshade, ancient home to demons. It’s said that only those with a taste for danger and darkness dare to venture there.
The landscape perfectly suits these malevolent creatures with its twisted trees and murky swamps. Ruling over this dark world with an unyielding iron fist is Vesper Villainous, the Demon King of the Darkbourne. His reign has been long, but he shows no signs of slowing down – after all, who wants to challenge an 8000-year-old demon?
Content in his solitude, Vesper has long given up on finding a mate. After all, it’s rare for demons to be blessed with a life partner. In his younger days, he searched far and wide for his destined one, but repeated disappointment hardened his heart.
Now, Vesper’s existence centers around his formidable crown and maintaining a sanctuary for demons on the brink of extinction.
But everything changes one fateful night under the brilliant full moon when Selene Lunaire, a celestial nymph, wanders into the forbidden forest. Vesper can’t resist her intoxicating scent and embarks on a mission to find her.
Sensing a demonic presence watching her every move, Selene boldly calls out to her observer and demands they reveal themselves. The only answer she receives is being swept into the air by invisible arms and carried toward the ominous Castle Darkbourne. Little does she know, her fate is about to take an unexpected turn in this wickedly whimsical tale of fated mates.