—Frederick explaining about the Exalt, Emmeryn, to the Avatar.
The Mark of Naga which is commonly found on the body of the Ylissean royalty.
The Exalt is the title given the ruler of Ylisse. Those who are descendants of the Exalt are known as the Exalted Blood.
Profile
The Exalt rules from the city of Ylisstol. All descendants of the Exalt have the Mark of Naga, more commonly called the "Brand of the Exalt", somewhere on their body, symbolizing the family's ancient pact with Naga, leader of the Divine Dragons. This Brand may not appear at birth, but eventually the Brand will surface somewhere on their skin. However, in rare cases, no Brand may surface. The child of an unsurfaced-Brand individual may inherit a Brand of their own.
The Ylissean royal family safeguards two national treasures: the Falchion and the Fire Emblem. The Falchion can only be used by those of Exalted blood, however the sword is selective on whom can wield it even among Exalted blood. The Fire Emblem is a sacred artifact which is necessary in order for one to perform the Awakening ritual to unlock the true power of the Falchion.
History
The bloodline of the Exalt traces its origins to the Hero King Marth. 1000 years before the start of Awakening, during a period known as the Scism, the first Exalt was granted the power of Naga which allowed him to unlock the Falchion's true power and sealed the Fell Dragon, Grima. In the years following Grima's defeat, the Exalt formed the Haildom of Ylisse and the followers of Grima set up the rival country of Plegia, while the rest of the continent eventually became part of Regna Ferox. Because of the Fire Emblem's vast powers, four of the five gemstones were removed from the Emblem and distributed across the land. Ylisse still held onto the now weakened Fire Emblem which had only the silver gem, Argent, left on it as well as the Falchion.
Over the next thousand years, Ylisse and Plegia went to war relentlessly for their respective worship over the Holy Dragon Naga and the Fell Dragon Grima. Emmeryn, Chrom, and Lissa's father lead a particularly brutal campaign which nearly destroyed the Halidom and Plegia. 15 years prior to the start of Awakening, the previous Exalt died suddenly. At the age of 9, Emmeryn assumed the role of Exalt. Though she experienced much ire from her people, Emmeryn eventually ended the war and restored peace to the Halidom. The Ylisseans were grateful for this newfound peace and Emmeryn became a beloved Exalt and became a symbol of the peace in the realm. Despite the newfound peace for Ylisse and its new Exalt, Plegia was still seething from the war which nearly destroyed their nation. Their king, Gangrel launched numerous attacks upon the Ylissean border for 15 years during Emmeryn's rule in an act of vengeance for what Ylisse had done.
Pressured by Plegia's constant attacks on their borders, Chrom formed the Shepherds, a group of vigilantes who help quell the Plegia uprising. Emmeryn sought help from Ferox to help stop the Plegian army. Even with the aid from them, Emmeryn is nearly assassinated one night. For her safety, Chrom advises that she leave the capital but after barely leaving Ylisstol, Gangrel attacked Ylisstol. Emmeryn leaves to return to Ylisstol in hopes of parleying with Gangrel. Before she leaves, she hands Chrom the Fire Emblem because it holds extreme importance for the sake of the world. Emmeryn is then captured by Gangrel and is sentenced to death in Plegia. Chrom and the Shepherds make it to the Plegia Castle Courtyard and nearly rescues Emmeryn with help from the Pegasus Knight Squad from Ylisse. However the plan quickly fails when Aversa summons archers and kills the Pegasus Knights. Gangrel tells Chrom to either hand over the Emblem or have Emmeryn killed. Chrom finds that Emmeryn's life is too important to give up over the Fire Emblem and nearly gives up the Emblem. However, Emmeryn sacrifices herself to protect Chrom and make sure that the Fire Emblem does not end up in Gangrel's hands. In the aftermath of Emmeryn's death, Chrom leads his army to end Gangrel once and for all. After defeating Grima, Chrom becomes the new Exalt.
In the alternate timeline, Emmeryn was assassinated in Ylisstol rather than at Plegia Castle. Chrom still became the Exalt, but he was gravely wounded during the assassination. Later, this wound would lead to his eventual death when Grima possessed his suitable vessel. With the eventual death of Lissa, only Lucina, her sibling, and Owain live, leaving them as the last Exalted Blood. Naga guides the children back into the past in hopes of altering the future by defeating the Fell Dragon once and for all.
In the Future Past storyline, Lucina and the children manage to recover the Fire Emblem and the 5 Gemstones, allowing her to perform the Awakening. Lucina is granted the power of Naga and seals the Fell Dragon once and for all. In the aftermath, Lucina becomes the new Exalt of Ylisse.