The events in Tower of Dawn take place simultaneously with the events in Empire of Storms.
Chaol Westfall is a lord of Adarlan, and for years, he served the evil king as captain of the royal guard. Everything changed when Chaol escaped the king, leaving his best friend, Prince Dorian, in his father’s clutches. Chaol aided the rebel movement, and the king hanged all the soldiers who helped him. Aelin and Chaol rescued Dorian, but the king used his immense Valg power to shatter Chaol’s spine, an injury that no healer has been able to fix.
Dorian kills his father and is freed from the control of the Valg prince that had possessed him. He appoints Chaol to the position of hand of the king, while Aelin appoints him as an official ambassador to Terrasen. Dorian and Aelin ask Chaol to journey to the mighty empire in the southern continent to both seek help at the Torre Cesme, the legendary tower that hosts the academy of healers, and to ask the khagan to ally themselves with Dorian in the upcoming war against the Valg.
Chaol is accompanied on the long voyage to the city of Antica by Nesryn Faliq, the new captain of the guard and his former lover. While they both care for each other, Chaol’s anger about being confined to a wheelchair and intense guilt over past mistakes won’t let him get close to her.
When they arrive at the vast palace, Chaol and Nesryn are introduced to the royal court consisting of the khagan, Urus, and his children: Princess Hasar, commander of the naval fleet; Prince Sartaq, commander of the aerial cavalry of ruks, large birds; Prince Arghun, the politician and spy master; Prince Kashin, commander of the horse cavalry; and Princess Duva, the younger princess who is happily married to a foreign prince and is expecting her first child.
Chaol wants to secure a partnership right away, but he and Nesryn are told that the khagan’s youngest child, Tumelun, has recently committed suicide, and the family is in mourning. An alliance between Erilea and the southern continent will have to wait for a more appropriate time. Chaol does not think he has time, especially when Arghun reveals that Duke Perrington’s forces have sacked the city of Rifthold and that Dorian is missing.
Privately, Prince Kashin tells Chaol that he thinks Tumelun was murdered and believes Duke Perrington may be involved. He asks Chaol to quietly investigate his suspicions. Chaol also starts therapy to heal his broken spine with the help of a young woman, Yrene Towers.
Yrene is a magically gifted healer with immense powers. She is a refugee from Fenharrow, land that was captured by Adarlan. She has an intense hatred of Chaol for serving the king. Nevertheless, Yrene agrees to heal Chaol as the last assignment for her training as a healer.
When she uses her healing magic on Chaol’s back, she encounters the dark magic of the Valg. Determined to find out more about the evil that won’t allow Chaol’s back to heal, she does research in the Torre Cesme’s ancient library, only to be stalked by a presence she feels but doesn’t see. Yrene escapes the presence, but another healer is killed. Her body is left as a dried-out husk.
Chaol and Nesryn know this is a sign that the Valg are in the southern continent. Nesryn and Sartaq investigate the murder but find nothing. At first Chaol won’t give Yrene any information about his injury, but this changes after she is stalked.
He thinks the Valg want to stop her before she discovers how to heal him, so the pair begin to work together. With more understanding, Yrene uses her magic to push back on some of the darkness that lies within Chaol. Through hours of physical and magical therapy, Chaol walks with the help of a cane.
Sartaq travels to the mountains of the rukhin to seek answers from the bird flyers, which have lived there for eons, and Nesryn accompanies him. The leader of the riders, Houlun, tells Sartaq and Nesryn that the enormous and intelligent spiders who share the mountains with the rukhin have been stirring and have recently stolen ruk hatchlings. Houlon tells them that thousands of years before, a Wyrdgate opened in the mountains and the Valg spiders came through. The Fae came to the mountains to defeat them and to teach the ruks how to fight. The Fae left outposts behind.
Nesryn, Sartaq and a shapeshifter, Falkan, go to investigate. As they see a ruk hatchling trying to escape, Sartaq’s ruk tries to rescue the chick but it’s a trap. Nesryn and Sartaq are captured and tied up. A spider tells Sartaq the truth about the Valg.
The spiders originated from the Valg home world. They were created by the Valg queen Maeve and served as her handmaidens while three Valg kings waged war. Maeve eventually married the Valg king Orcus, but she was dissatisfied with her life. She learned how to cross through Wyrdgates to other worlds. The spiders followed her. Eventually, Maeve found Erilea.
Maeve found the Fae, the oldest inhabitants of Erilea, ruled by two Fae sister-queens, Mab and Mora. Maeve bound her essence into a Fae body and hid her true Valg form beneath. She used her abilities to get into the minds of the two queens and made them believe they had an older sister. She took the name of Queen Maeve of the Fae. When Maeve, Mab and Mora returned to their palace, she altered the minds of every creature until all beings in the realm of Erilea knew that the Fae were, and always had been, ruled by the three Fae sister-queens. She killed those who resisted her power.
Orcus discovered that Maeve had left through the Wyrdgate and removed three slivers of the realm doorway, Wyrdkeys, to control the opening and closing of the Wyrdgate. Each Valg king had a key, and they searched for Maeve through the realms. When they reached Erilea, they found the Fae ruled by Maeve, Mab and Mora.
The Valg armies fought against the Fae armies, but the Valg kings did not recognize Maeve in her disguise. She used knowledge of the Valg armies to defeat them. Maeve stole the Wyrdkeys and banished two of the Valg kings back to their realm. Before she could banish Erawan, Brannon Galathynius stole the keys, leaving Erawan in Erilea.
Falkan, in the shape of a rodent, chews on the bindings. Falkan frees Nesryn and Sartaq, and they escape the spiders. They journey back to Antica to share what they have learned.
While Nesryn is traveling with Sartaq, Yrene works to fully heal Chaol and find out more about the Valg from the ancient papers buried deep in the Torre Cesme’s library. They discover that magical healing powers, granted by the goddess Silba, were brought to the southern continent by the Fae thousands of years before and bred into humans in the area.
Silba’s healing magic can rid anyone of Valg possession. It removes the Valg demon, which behaves like a parasite. When the Valg creature's true form leaves the host body, it withers and dies in sunlight.
Yrene realizes that the Valg parasites thrive on anger, hatred and fear. She chooses to forgive Adarlan for what its soldiers did to her family and her people, and then she treats Chaol. To be fully healed Chaol must forgive himself for his failed relationships with Aelin and Nesryn, and his failure to protect his soldiers and Dorian when they needed him most. Chaol is fully healed only after he lets go of his self-loathing and anger.
Chaol is armed with the knowledge that healers can drive out Valg possession, information vital in the upcoming war. The gifted healers of the Torre Cesme are just as important as soldiers. Before he can share this, the Valg lure him and Yrene into the catacombs beneath the Torre Cesme to kill them. They discover that Princess Duva is possessed.
Duva received a Valg ring as a wedding present from Duke Perrington and has been possessed since her wedding day. When her younger sister, Tumelun, suspected that something was wrong with Duva, the Valg inside pushed her from a balcony, making her death look like suicide.
Chaol fights Duva, but does not want to kill the pregnant princess. Duva uses that advantage and breaks Chaol’s body. Sartaq and Nesryn arrive, but it’s Yrene who incapacitates the princess. Chaol is near death, so Yrene prays to Silba for healing. The goddess grants her request, linking Yrene’s life to Chaol’s. When one dies, so will the other, and Chaol can only walk with the help of Yrene’s magic.
Yrene uses her magic to rid the Valg parasite from Duva’s body. The royal family is so overjoyed, the khagan grants Yrene a boon. She asks him to save her people. Chaol marries Yrene, and they sail for Erilea with the might of the khagan’s armies and healers from the Torre Cesme. The khagan names Sartaq his heir, and Sartaq asks Nesryn to rule with him after they return from war.