Garon is the previous king of Nohr (before his eldest son Xander succeeded him in 2 of 3 routes) and is the primary antagonist of Fire Emblem Fates Birthright, Conquest and Revelation. Originally, he was a stern, but fair man, according to his son Xander, but was then consumed by a great evil who clouded his fair sense. He worships the silent dragon, Anankos, more than the dusk dragon, and is the father to Xander, Camilla, Leo and Elise. He is the husband of Queen Katerina, Queen Arete and three other Queens and step-father of Azura.
Before his daughter Elise was born, The Real King Garon is a gentleman and kindhearted person. He give his 4 children including Azura piggyback rides and deeply cares for his wives especially Arete the most. After his first wife, Katerina died, He remarried to Azura's mother, Arete and made her as his second wife after he falls in love with her by her talented singing. He cares for his children including his step-daughter, Azura. After Arete's death, He suffer the loss of her. He continue to become the benevolent king to his family and subjects.
After Elise was born, He died shortly and later was resurrect and controlled by the silent dragon, Anankos. He become corrupted and merciless as a serveant to Anankos. He originally want to rule over Hoshido. After he killed Sumeragi, he capture Sumeragi's step-child, Corrin, and made adopted him/her as his child and made Corrin lost memory his/her past. Later He wants to destroy not only Hoshido but Nohr too and wanted to rule over Valla.
Garon was formerly a loving father to his children, but was turned evil by Anankos. In Conquest, it is revealed Anankos had replaced him with a literal monster that normally appeared human. Before the events of Fire Emblem Fates, Garon proposed a peace meeting between himself and the king of Hoshido, Sumeragi, who expected to finally stop all conflict between the two kingdoms. Upon arrival with his child, Sumeragi is brutally wounded by Garon's army of archers. Garon killed Sumeragi and takes the child, and raises them in a secluded fortress.
Before making the choice of which kingdom to join in Fates, Garon sees that after many years of being trapped from the outside world, that his 'adoptive' child is ready to get involved in Nohr's army. Their first task is to kill two prisoners, a task which to Garon sounds easy, but to his child impossible. He finds killing amusing and gets angry at those who don't do it upon request. His biological son Leo steps in and pretends to kill them, satisfying Garon's wants.
Due to them not performing their father's set tasks, the avatar joins Elise in apologising to their father, and they are surprised to be forgiven so easily, but with a catch. To prove their alliance, his adoptive child must go on their first military mission to the outskirts of Nohr, close to Hoshido's borders. He grants them a blade named Ganglari.
He sends the convicted murderer Hans along to help his child, despite his other children's skepticism. Upon arrival to the site, the Nohrians are put before Hoshidan soldiers, who would not harm them unless provoked. The avatar agrees, but Hans does not, and brutally kills one of Hoshido's soldiers. This provokes the Hoshidans which makes them attack, but they are later defeated. Hans is then placed before the avatar's dragon form and explains that he was only following Garon's orders, which shows that he wanted his child to be killed. However, instead of dying, they are kidnapped by an ally of Hoshido, Rinkah.
Garon himself is not seen again until Chapter 12, where the avatar reaches Cyrkensia. They plan to kidnap Garon at the opera house Garon is at. Zola, a former underling of Garon's, puts a spell on Azura so she appears to be the famous dancer Layla. Azura's song causes Garon discomfort due to its nature, and Garon sees through Zola's spell. Zola askes Garon to spare the avatar due to their kindness. Garon, however, views this as an act of treason, and executes the mage before the player's army and Elise's eyes. The avatar's army escapes.
The avatar's group breaks into the castle, defeating Camilla and killing the Nohrian generals Hans and Iago, as well as Xander. When they reach the throne room, Garon taunts them and calls his own children "pawns for the war." The avatar, knowing Garon cannot be reasoned with, attacks, but their sword cannot penetrate his armor. Garon attacks the avatar, Azura, and Ryoma, and tells them to surrender. The avatar's Noble Yato sword is transformed into the Blazing Yato, which can harm Garon. Their armies clash, and Garon is defeated. He refuses to die, using Anankos's power to transform into a dragon. The fight continues, and Azura uses her song to weaken him. He is killed, and hints that he had been long dead, before dissipating into water.
Garon is shocked and angered that the avatar returned to Nohr, knowing that while they were in Hoshido, s/he learned of their kidnapping at a young age, agreeing with his subordinate Iago that they could be a Hoshidan spy and orders Xander to kill them. When he refuses, Garon decides to confide with Anankos through an effigy in the ceiling. After doing so, he sends them alone to the Ice Tribe Village to quell a rebellion. His true reason to do so was to make them suffer. Overhearing this, Xander sends Silas, Elise, Arthur, Effie, and Felicia/Jakob (depending on gender) to assist them. After their successful return, Iago informs Garon that they were assisted, causing the latter to nearly execute the avatar for their disobeyal. Elise and Xander step in, informing Garon that they were responsible for assisting them. Giving the avatar another chance, he sends them to capture Notre Sagesse and to crush the rebellion in Cheve. Before this is done, they reunite Garon with Azura, his step-daughter. He cares little.
After the uprising is put down, Garon and his children travel to Cyrkensia to watch Layla, a favored dancer, perform. During the performance, a "mysterious" songstress curses Garon, causing him extreme discomfort (similar to the Birthright path). Before she can be captured, Kumagera and a band of Hoshidan soldiers arrive in an attempt to assassinate the king of Nohr. The soldiers are defeated and Garon recovers. He proceeds to order the avatar to kill all the singers in Nestra. When they protest, Leo intervenes to prevent Garon from attempting to execute them (again).
Shortly afterwards, Azura speaks to the avatar with a one-time-use crystal ball. She tells them that Garon died long ago and that he was being possessed by "a demon" to spark the war of the two countries of Nohr and Hoshido. She claims that if he were to sit on the throne located in Castle Shirasagi, he would degenerate into a slime form.
Later in the game, Garon leads the invasion of Hoshido, along with Iago to a lesser extent. After defeating Ryoma (followed by him commiting seppuku), Iago (betrayal) and Hans (betrayal), Garon arrives at the Hoshidan throne, asking his children to wait outside. When they open the doors, Azura's claims were found to be correct; instead of Garon, they encountered a slime monster. After he summons a group of mysterious soldiers to kill them (again), and is killed shortly afterwards.
It is revealed that the real Garon had died shortly after Elise's birth and the Garon present is a servant of the King of Valla, Anankos, who is little more than a corpse imbued with a semblance of life by Anankos' power. His mission is to destroy both the kingdoms of Nohr and Hoshido for "betraying" its master. The undead Garon makes less appearances in this route compared to the other two routes.
In his first appearance in the cutscene before Chapter 9, he is seen speaking to his stone effigy of Anankos on the ceiling, a little surprised about the fact the Avatar survived the earlier explosion at Hoshido and knowing the truth of the entire situation. He decides that the Avatar being afraid and wanting them to suffer is not enough, and that decides that the Avatar simply will have to be disposed of. He then erupts into maniacal laughter.
In his second appearance before the start of Chapter 14, Xander and Leo arrive in the throne room and see Garon looking manipulated, telling them to continue the war against Hoshido, and tells them that he wants to destroy not only Hoshido, but also Nohr itself. This causes both Xander and Leo to reconsider their earlier dismissals of the Avatar's claims about Garon being manipulated by the real culprit, the Invisible Kingdom of Valla, and they eventually join the Avatar's cause.
He makes his last appearance after Anankos' defeat in Chapter 27 of this route, offering to become a vessel for Anankos in place of Gunter, only for Anankos to eat him to reclaim the power he gifted to Garon to obtain his full power again.