Prelude of Thracia 776
This section covers the events that serve as context to the game's events. It is a complete compilation of facts and events given by 3 main sources: the first is information provided by the game, the second are events (and spoilers) from FE4, and the third is Leonster's Fall, a short novel written by the game's developers which was included in the “Fire Emblem: Thracia 776 Illustrated Works” book.
The story takes place in the Thracian Peninsula, a territory that was born a unified kingdom under the rule of the twin crusaders: Dáinn and Njörun. This kingdom would last until roughly 100 years before the events of the game, when bad blood between the crusaders' descendants caused its split and the birth of 2 separate nations: the Munster Province to the north, and the Kingdom of Thracia to the south.
In the year 760 of the grannvalian calendar, Prince Quan of Leonster returns home after a long journey of helping his lifelong friend Sigurd. After staying in his dominion for a year, Quan gets approval and support from his father, King Kalf, to once again ride off in Sigurd's aid, this time bringing with him half of the Lanzenritter: Leonster's royal army. His wife Ethlyn, Sigurd's younger sister, not only insists on going, but also pleads to take their young daughter Altena on their journey. Quan vehemently declines, but gives in after Ethlyn promises to go home when they arrive at the Aed Desert, being worried about their youngest son Leif, who was just a newborn, being left behind in Leonster.
As Quan and his troops arrive in the desert, they are suddenly ambushed by the dracoknights of Thracia, led by King Travant himself. The Lanzenritter are completely massacred, with Quan being the only one able to put up a fight thanks in part to the holy lance Gáe Bolg. However, as Travant picks up Altena from the hands of Ethlyn's corpse, he orders Quan to surrender the Gáe Bolg unless he wants his daughter to share their same fate. And thus, Quan faced his demise at the hands of Travant.
Shortly after Quan and Ethlyn's untimely demise, Sigurd's army also fell, in what would become known as the Battle of Belhalla.
Peace does not last, however, as only a year later, the entire Munster Province finds itself under attack by Thracian forces, hellbent on conquest.
With Connaught betraying them, Leonster's king falling in battle and Ulster still unwilling to act, soon enough Castle Leonster finds itself under a massive siege that ends with the castle in flames and the near extermination of Leonster's knights.
After Thracia's crushing victory, Travant's ambitions quickly crumble as the Grannvale Empire arrives at their doorstep, wishing to take the Munster Province as part of their continental conquest.
Meanwhile, after leaving Castle Leonster behind, Finn, Leif, Nanna and Lachesis find shelter in Ulster, but 2 years later they are forced to flee after being discovered by the Empire. Because of his actions, King Ulster is executed and Princess Miranda is put into house arrest, while the fate of Queen Ethniu is unknown.
After this, they come to the village of Hrest where they stay for another 2 years. Here, Leif befriends a young boy named Asbel. However, they are soon betrayed by its citizens and have to flee once again, to the independent city of Tahra, where Leif meets the Duke and his daughter, Lady Linoan.
After travelling through many towns and villages, Finn is gravely injured after fending off some of their pursuers. It is then that they arrive in the village of Fiana, led by a swordmaster named Eyvel who welcomes them as if they were her own kin. Here, Leif and Nanna are able to spend 3 peaceful years alongside children of common birth such as Osian, Halvan, and Mareeta, Eyvel's adoptive daughter. Together, they join the Fiana Freeblades, a local militia founded by Eyvel to protect nearby villages from pirates and brigands.