Thracia 776 takes place during the events of Fire Emblem: Genealogy of the Holy War. During Genealogy of the Holy War, in the year Gran 761, the ruler of Grannvale, Arvis has expanded his country's rule across the whole of Jugdral. Thracia 776 is set between Chapter 5 to Chapter 8 of the second generation storyline, while the exiled prince Seliph is still in hiding and preparing to battle Arvis's hold on the continent.
In the Thracian peninsula in southeastern Jugdral, the Munster District was subjugated following the deaths of Prince Quan of Leonster and his wife Ethlyn in the Aed Massacre. However, shortly after capturing it, Thracia was defeated by Grannvale and forced to cede control to Friege, becoming a servant state to the empire. Leif, the deposed heir to the Republic of Munster, who was rescued from an attack by the forces of Thracia by Finn, a friend of Seliph's father Sigurd, starts a revolution against the Empire's occupation of the Munster District.
Several characters from Genealogy of the Holy War return, such as Finn, Diarmuid, Ced, and Nanna, while others appear as cameos, such as Seliph (the main protagonist in part 2 in Genealogy of the Holy War), Julius, Julia, Altena, Coirpre, and Hannibal. Some original characters are also introduced, such as Halvan, Orsin, Lifis, Shiva, Dagdar, Machyua, and Mareeta.
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