The Primal of Blood and Bone by Jennifer L. Armentrout

Here i a summary with spoilers for The Primal of Blood and Bone by Jennifer L. Armentrout

In the wake of a Revenant attack and Cas’s transformation, Poppy’s eyes snap open, full of silver and eather, but she doesn’t fully wake. Instead, the eather in her spreads and lashes out, striking both Kieran and Casteel, knocking them unconscious for a couple of days. When they wake, Poppy is still in stasis, but the two of them feel slightly different.

While Poppy sleeps, Cas won’t leave her side, but the outside world is changing, and their new king and queen have not made an appearance. Cas tries to rule from Poppy’s side, while Kieran manages the new city and relays information to him. Many Ascended must now choose where their loyalty lies, and another major problem arises: multiple Ascended are found dead, drained of blood. Cas fears, though hopes he is wrong, that it’s Kolis trying to gain enough strength to get a real body. This suspicion is confirmed after he speaks with Reaver, who tells him about a vessel—a way for a spirit to join with a body. That’s when they begin to wonder why Isbeth was so desperate to get Poppy back. As they discuss this, Kieran arrives with troubling news: the sun has not set, and the rotation now seems to be going in the opposite direction.

Meanwhile, Poppy dreams. She’s trapped in a golden cage she cannot escape. A man appears and speaks to her, but she finds she cannot respond. No matter how much she tries, she cannot, until she realizes she is speaking to Death. In another dream a few days later, she sees the man again. At first she trusts him, but then she doesn’t—she knows the name Cas. However, Cas quickly shifts into another she knows all too well, Duke Teerman, and it terrifies her.

When Poppy wakes, she cannot tell what is real and what isn’t. She sees the man she believes is Cas, someone she knows is important to her, but she’s constantly reminded of both his love and Duke Teerman’s cruelty. She realizes she needs to feed but fears she will hurt Cas if she does. Cas, relieved she’s awake, convinces her to feed from him, and she does. But when Reaver arrives, he declares something is wrong with her. He rips her away from Cas and insists that Kolis is inside her. As Kieran enters, the three clash, while Poppy struggles but knows something is wrong. She looks at Kieran and tells him it’s time for his promise: she wants him to put her back into stasis for the long sleep. Cas is furious that Poppy and Kieran made this decision without him, and in his rage, he tells Kieran to leave and never return. Reaver knocks Poppy out, and though it breaks Cas, they lock her in a cell—if she or Kolis wakes, they won’t know where they are. Cas keeps watch as she wakes now and then, always battling herself. He realizes he has only spoken with Kolis, never the real Poppy. Eventually, Reaver declares he must go to Iliseum to seek help from a primal.

Days later, a primal who looks like a Da’neer arrives, introducing himself as Attes. He instructs Cas to search for a mark Kolis left on Poppy. To Cas’s horror, he finds one between her breasts. With Attes’s help, they use dragon blood to burn it out. They watch the mark vanish, hoping it took Kolis with it. Poppy falls back into sleep, but they still fear Kolis will find another body.

Eventually, Poppy wakes. She and Cas reunite, she feeds from him, and they catch up on everything that happened while she was unconscious. But before long, Poppy senses massive death. A portal opens, and she steps through, leaving Cas behind. She finds herself in a realm of destruction, what appears to be New York City. Stunned by the people, she blacks out. Meanwhile, Cas panics, unable to reach her, until a Fate named Aydun comes to calm him.

Poppy wakes in Iliseum, surrounded by Fates, including Vikter, her father figure. They confirm she is an Ascended Primal. Because of the joining, Cas and Kieran are also Ascended Primals, but their type—Deminyen—means they owe no loyalty to any court, leaving them unchecked. The Fates worry about Cas most of all, fearing his temper and obsession with Poppy could cause catastrophic destruction. They tell Poppy she must defeat Kolis or the world will fall apart.

When Poppy returns to Cas, she realizes what she did was shadowstepping. The two share everything again, but she senses tension between Cas and Kieran. Reaver then arrives and asks Poppy to help wake Jadis. Despite her efforts, Jadis does not stir.

There’s no time to dwell. Soon, more bodies are found, this time children among them. When Poppy insists on seeing for herself, the corpses reanimate as gruls and attack. During the fight, Poppy notices Kolis’s eyes in one of them. He calls her solis, “my soul,” before Cas kills him, ending the attack. Realizing Kolis will not stop, Poppy and Cas decide it’s time to strike first.

Poppy reconnects with her old friend Tawny, but mid-conversation realizes something is wrong: when she ascended, she took part of Tawny’s soul, and now it is lost.

Kolis attacks again, this time unleashing sea monsters. Desperation grows until a primal named Rhahar arrives, temporarily subduing Kolis. But it’s revealed to be a trap—Illiseum was the true target. Soon after, an earthquake shakes the realm. They learn Rhahar has died.

Reaver announces the arrival of Seraphina, the true Primal of Life. She confirms what they’ve learned and helps bring Jadis back, though in a weakened state that devastates both Reaver and Seraphina. Before leaving, Seraphina tells Poppy a terrible tale: Sotoria, Kolis’s first love. Obsessed with her, Kolis tried to steal her soul after her death. Seraphina trapped it in a star to prevent resurrection, but Isbeth uncovered it, bringing Poppy into the world with Sotoria’s soul. Seraphina gives Poppy a knife capable of killing Kolis, telling her she alone can end him. Poppy passes her old blade—made from Delano’s sister’s bones—on to Delano.

Malik returns from scouting with news of a group of Ascended who drink only animal blood. Among them is Ian, Poppy’s brother.

Cas’s father finally returns, bringing word from Kolis: he is coming, and if Poppy refuses to submit, he will force her to. With this new threat, Attes joins them, though Cas mistrusts him for the way he looks at Poppy.

Poppy begins waking at night, drawn to the Cliffs. Sometimes she doesn’t realize she’s doing it. One night, she sneaks out and finds a Revenant, who allows Kolis to speak through him. He taunts her with memories of her childhood, admits to terrible manipulations, and promises he will take her soul. She fights him, and with Attes’s help, kills the Revenant.

After the defeat of Isbeth, Poppy and Cas prepare to address their people, but are interrupted by the appearance of Isbeth herself—or something that looks like her. Enraged, Poppy loses control and terrifies her people before Cas calms her. Isbeth delivers Kolis’s message: meet him in his realm tomorrow with a Fate present, or the city will be destroyed.

A council forms. Poppy insists she must go alone. The Fates’ words suggested they would not protect Cas or Kieran. Cas argues furiously, and reveals Poppy once asked Kieran to put her down if necessary. Their fight ends with Cas storming away. Poppy, certain he’ll follow despite her wishes, summons the Fate Thorne and makes a deal: he will stop Cas from following, in exchange for a future favor.

The night before, she writes two letters—one to her missing sister Millicent, and one to Tawny. Cas appears at the last moment, and they share a kiss as Poppy promises she will return.

Poppy and Attes enter Kolis’s realm, finding him waiting without a Fate to mediate. He taunts her with more revelations about her childhood. She strikes with Seraphina’s knife, but it fails. Kolis overpowers her and reveals his plan: he will break her, drain her, and take her soul to resurrect Sotoria. He begins feeding on her until she blacks out.

Meanwhile, Cas unravels. He lashes out, cruel and reckless. When Kieran confronts him, Cas attacks until suddenly he blacks out from pain. Awakening ten minutes later, he feels the bond with Poppy fading. Panic sets in as singing fills the air—wolven begin killing themselves under its spell. Cas even has to break Kieran’s bones to stop him. As bodies fall, Kolis appears, declaring Poppy gone. In the fight, Hisa, Delano, and Valyn are killed. Cas unleashes his full power, his body shifting, silver bones breaking through. Kolis escapes badly wounded. Consumed by rage, Cas explodes with eather, vines tearing through the castle, ravens circling. He becomes death and destruction incarnate.

Days later, Kieran is left with the wreckage. Poppy is still missing—though Attes swears she’s in Iliseum. Funerals are held. Cas is broken. Kieran brings his father for help, but on the way they encounter Millicent, who has mysteriously returned. She claims to bring a gift: Callum. Kieran reflects on the prophecy—Poppy was the Harbinger, Kolis the Great Conspirator. But the death and destruction destined to come would not be Kolis’s doing. It would be Casteel’s.

When Kieran enters the throne room, he finds only a shadow of the man he once knew. Cas is no longer himself. He is the Primal God of Death and Destruction.