King of Scars follows Nikolai Lantsov, the young king of Ravka, as he attempts to rebuild his war-torn country. Despite his charming and confident persona, Nikolai is haunted by a dark secret: he carries a dangerous curse inside him, a remnant of the events that transpired in Ruin and Rising from the Shadow and Bone trilogy. The curse, which involves a monstrous, demonic force living within him, threatens to consume him and his kingdom. As Nikolai struggles to control the curse, he faces numerous challenges, both external and internal. He must navigate political intrigue, dangerous alliances, and attempts on his life while trying to keep his kingdom stable. Meanwhile, a group of unlikely allies, including Zoya Nazyalensky, a powerful Grisha, and Nina Zenik, a fan-favorite character from the Six of Crows duology, are drawn into the conflict, each with their own personal struggles. The novel explores themes of power, sacrifice, and identity as Nikolai must confront his inner demons while trying to be the king Ravka desperately needs. Bardugo's world-building and character development are rich and intricate, bringing the Grishaverse to life in a new and exciting way.