I loved this series...my review goes through all 4 books. Overall, these are written very well. Lots of world building and action. The smut is smutty without being too much. I would definitely recommend to lovers of romantasy. There are a lot of fae creatures with different magic and abilities. The plot is good and well-written. The story flows easily although there were times that I skipped whole paragraphs to get to the meat.
**SPOILERS AHEAD**
It starts out when a baby girl is born to the king and queen of the Night Realm. Right after birth, the baby is kidnapped and everyone in the birthing room, including the queen, is killed. For years, the Night Realm searched for the baby, but all leads led nowhere.
21 years later and a new generation of hunters from the Night Realm is on the case. A group of men now named the Nighthounds, are searching for new leads. They finally got a promising lead and find the lost princess shackled in chains in a dark cave in the Iron Realm, abused, tortured, raped, and malnourished. The Nighthounds kill the guards and rescue the princess.
During the long ride back home, the princess learns her name for the first time. Izadora. She learns about her family, how to use magic, how to fight, and new bonds form with her rescuers. One, in particular, she feels a close bond with. Kazimer and Izadora feel a tug between them that is irresistible. She learns that her magic is white and learns that there was a prophecy made a millennia ago about a baby born with white magic. She will bring the realms together. By the time they get to Kazimer's home outside of the capital of the Night Realm, they become lovers. They stay at Kazimer's home for a few weeks to recover from the long travel and to let Izadora's father know that they've finally found her.
However, once they take her home and she meets her father for the first time, he's anything but a loving father whose daughter was just returned home to him. He's manipulative and not a good man. Izadora sees him for who he is and plans to overthrow him to take the seat as Queen. Before she can do that, a group from the Iron Realm bursts in on the homecoming feast, announces that the kings of the two realms, the Night Realm and Iron Realm, were in on this plan together, and that the princess was promised to the prince of the Iron Realm when she came of age. Izadora is outraged. She slits her father's throat before she's kidnapped, once again, by the Iron Realm.
On the way back to the Iron Realm with the prince, Ruslan, she learns that he is her supposed mate, not Kazimir. She hates him but feels a magnet between them pulling them together. Over the coming weeks, she starts to learn about how the two realms conspired together and that he, Ruslan, had no idea of the tortures she was enduring through the years. They conspire to kill the king of the Iron Realm for his abuses as she did in the Night Realm and they will rule together to unite the kingdom for all creatures.
Meanwhile, Kazimir and his group of Nighthounds gather their hunting party and goes to rescue Izadora again. On the way through the realms, Kazimir receives a gift from the Fates, Binding Magic. It's a form of black magic that has driven others before him, mad. He changes, and not for the better. He's obsessed with Izadora and believes they are mates. He will get her back during Beke, a kind of festival that is hosted by a different Realm each year for friendly competitions and the like. Nobility and common folks alike from all the realms will be in the Iron Realm for this 2-week festival so this will be the perfect opportunity. His friends see the changes in him and do not like what he is becoming but they follow him as brothers. They've been friends since birth so they will trust his leadership, much to their detriment later.
Izadora and Ruslan are falling in love, and she accepts that both Ruslan and Kazimir both may be her mate. The prophecy says there are two mates and she must choose between light and dark. Ruslan is everything she could dream of a mate to be. Kind to her, loving, takes care of her, and lifts her up instead of trying to hold her down. By the time that Kazimir and other nobility arrive in the Iron Realm for Beke, Ruslan and Izadora has killed the king and Ruslan is now King. They plan to wed but they have not yet accepted the mating bond. Ruslan gives Izadora space to figure out what she must do.
During the days of Beke, she sees that Kazimir has changed and is not who she once loved. He does despicable things and his obsession with her just makes her cringe. She finally chooses, and it's not Kazimir.
A war ensues in the final book where kings will be killed, and rivers of blood will flow.