Once upon a Demon's Heart: Cruel Fates Duet, Book 1

Name: Once upon a Demon's Heart: Cruel Fates Duet, Book 1
Price: 11.4 USD
Availability: InStock
Rating: 4.3 (6100 reviews)
Author: K. M. Moronova

by K. M. Moronova

4.3

About this book

Alira, a demigod knight burdened by the crushing guilt of a past massacre, finds herself trapped in a relentless time loop. Each iteration ends the same way: death at the blade of Kalel, the ruthless Blood Knight of the demon kingdom. After twenty cycles of agony, Alira decides to break the cycle by force, only to be thrust into an impossible alliance.

To avert a total war between their realms, she must enter a political marriage with the very man who has repeatedly ended her life. Kalel, a demon duke who feeds on the blood of demigods, harbors a deep, justified hatred for Alira rooted in the destruction of his kin. Yet, as they are forced into proximity, the lines between his thirst for vengeance and a burgeoning, forbidden obsession begin to blur.

Bound by a cursed union, the two enemies must navigate a treacherous landscape of political deceit and divine manipulation. As they peel back the layers of the realm’s history, they discover that their shared animosity may be a fabrication designed by the gods themselves. In a world where love is a weapon, Alira and Kalel must decide what they are willing to destroy to claim a future together.

Available Formats

Kindle: $11.40 Audiobook: $0.00

View on Amazon

What readers are saying

DivaSoldierFoster

He Killed Her 99 Times. She Married Him Anyway.

"This romantasy swept me away with its emotional depth, mythic stakes, and unforgettable characters. It’s a fast-paced, enemies-to-lovers tale that blends divine curses, political tension, and slow-burn romance into something truly unique. Alira, a demigod knight, is caught in a brutal time loop—dying again and again at the hands of Kalel, the demon Blood Knight. Her only escape? An arranged marriage to the very enemy who’s been her executioner. What follows is a tense, emotionally charged journey through guilt, power, and reluctant intimacy. The worldbuilding is rich with Roman-inspired mythology, dragons, dire wolves, and divine interference. Kalel is a standout: morally black, emotionally scarred, and impossible to ignore. Alira’s arc is equally compelling—her strength lies not just in battle, but in her ability to confront her past and choose a different future. “You are the only thing I’ve ever wanted that I wasn’t allowed to have.” This book is perfect for readers who love forbidden romance, morally complex characters, and stories that explore love as both a weapon and a salvation. I can’t wait to discuss the themes of fate, redemption, and emotional resilience with all of you. ["

November 30, 2025 Verified Purchase

Ashley

A slow burn that pays off

"I loved this book/author so much that I have started replacing her books with hardcover editions. This story is unique and keeps your attention from cover to cover. Maybe I am a sucker for K.M. Moronova, but I am 100% okay taking that to the grave. Her stories captivate me every single time, and I am hooked. With this story, the FMC is killed in a time loop for 20 years! I love it when you start to feel the characters really struggle with their feelings. This is more of a slow burn than many of her other books, but it is still a really good read. Can't wait for book two to come out. ["

March 24, 2026 Verified Purchase

Itzxraibooks

I need the second book

"“You should know that I die slowly with each tear you shed. I love you, Alira. I'm sorry for what I am.” 😭😭😭 K.M. Moronova writes like her pen is dipped in sin and sorrow, and this book is nothing short of a haunting poem I'll never forget. Her writing is equal parts poetic and seductive, aching with longing, laced with violence, and so rich in emotional texture that I swear I could feel the heartbreak soaking into every page. Alira and Kalel are two broken souls shackled by fate, reliving a nightmare that ends in her death over and over until something changes. But this time, something is different. There’s a shift, a hesitation, a look, a question and with that, the cycle begins to crack. The angst and yearning between them is unbearable in the best way. It's not just enemies to lovers, it’s executioner to lover, hatred twisted with guilt, and a desperate need to understand each other even as they tear each other apart. The yearning is constant and aching. Every touch, every glance, every moment of silence between them simmers with something forbidden and far too fragile. Kalel is everything I love in a monster brutal, cruel, and terrifyingly gentle when it matters most. Alira, my girl..... she’s carrying so much guilt and pain on her shoulders that you feel like she’ll shatter if she breathes too deeply. Watching her confront her beliefs, fall into the arms of her executioner, and still try to save the world, was rough. There’s something about the way K.M. blends spice with emotion, myth with brutality, that keeps me in a chokehold. The spice is deliciously unholy, (hello knotting scene) but never without purpose. Also, I’ve read every fantasy book she’s written, and I swear on the gods’ twisted games they all exist in the same universe. That’s my theory, and I will die on this hill. lol The ending was mean, and now I’m left staring at the wall, praying for the next book while mourning this one. 😭 ["

November 14, 2025 Verified Purchase

katvou

Great idea, but could have used more work and editing

"I had high hopes for this book, but unfortunately, at the end I was left disappointed. Not a bad book, but I was expecting and hoping for more. The idea sounded really interesting, a demigod stuck in a time loop where a demon kills her every time, but after 20 loops she’s had enough and ends up marrying said demon. Personally, I would have loved to see more world building, I know the book is short (about 250 pages), but even a little bit would have been great. Also, would have loved to learn what happened during those previous time loops, other than everyone dying. I didn’t feel the chemistry between the characters and felt like the heat scenes were used as a plot device to make it seem like there was something more between the MMC and FMC. Also, the pacing was a bit weird, and so many scenes ended abruptly with page or chapter breaks. So to sum up, great idea, but in my opinion the execution could have used some more work and editing. I’m still interested to read the next book and see what happens. ["

September 3, 2025 Verified Purchase