Fire Emblem Collision

Peaceful End: 3 Houses

White Clouds:

In the continent of Fódlan, Mercenary has yet another vision of a battle between 2 individuals, Nemesis and Seiros, and meets an amnesiac girl named Sothis. Awakening, Byleth tells their father Jeralt about the same dream she has been having for a while now. They soon rescue 3 nobles from a bandit attack. Edelgard, Dimitri and Claude, the house captains of the Officers Academy. In the process, Byleth almost dies saving Edelgard, but is able to turn back time thanks to Sothis. The 5 travel to the Officers Academy at the Garreg Mach Monatery, where Byleth is offered a position as a teacher, alongside other fellow teachers Manuela and Hanneman, and Jeralt resumes his former post as a high ranking member of the Knights of Seiros. The 3 houses are the Black Eagles, consisting of Edelgard, Hubert, Dorothea, Ferdinand, Bernadetta, Casper, Petra and Linhardt, the Blue Lions, consisting of Dimitri, Dedue, Felix, Mercedes, Ashe, Annette, Sylvain and Ingrid,and the Golden Deer, consisting of Claude, Lornez, Hilda, Rapheal, Lysithea, Ignatz, Marianne and Leonie,who was hyped to see Jeralt. Byleth chooses one of the three lords to take charge of and spends the next year teaching them the ways of battle and going on missions for the Church of Serios, run by Archbishop Rhea, getting to know every unique yet likable student. (at this point, you between the 3 houses, though the story remains the same no matter what house you choose). During all the teaching and training, with fun and drama in between, Byleth and her allies come to blows with forces conspiring against the Church, including "those who slither in the dark" and a masked individual calling themselves the Flame Emperor, with the emperor's identity unknown at this point. Byleth is soon introduced by Rhea's second in command Seteth and his younger sister Flayn.

Cindered Shadows:

After a bunch of events and conflicts, including the attack of the Death Knight that was instantly bested by Lysithea that dropped everyone's jaws, there had been rumours of a suspicious individual being seen around the academy, so Byleth and the house captains investigate. They wait until nightfall and follow them underground. They find themselves entering a passage that leads to an underground city beneath GarregMach Monastery, where they learn this figure is a part of the unknown 4th house, the Ashen Wolves, consisting of Yuri, Balthus, Hapi and Constance. After a fight, the Eagles, Lions and Deer demand their motives, so the Wolves speak of their house's history. It was first formed by a man named Aelfric approximately 15 years ago, as a group dedicated to protecting those who stumbled into this city known as Abyss. Despite its name, it is not recognised by the academy as a house, and unlike the other houses is not affiliated with any specific nation of Fódlan. They explain that mercenaries have been raiding Abyss recently, and ask for assistance from Byleth and the other students in protecting it. They soon meet Aelfric himself, who speculates that the mercenaries are after the Chalice of Beginning to conduct the Rite of Rising, an ancient ceremony which was once conducted by Four Apostles in an attempt to revive the goddess. So Byleth and the others agree to help the Ashen Wolves in retrieving the Chalice before it is snatched.

Upon retrieving the Chalice however, it is revealed that Aelfric was the mastermind behind the raids on Abyss and he planned to use the Ashen Wolf House to gather those with the blood of the Four Apostles so he could revive Sitri, Byleth's mother. But the ritual fails, which causes Aelfric and Sitri's corpse to fuse into a monster known as the Umbreal Beast. Byleth, Edelgard, Dimitri and Claude, joined by Yuri, slay the beast, and Byleth tells her students to not tell her father what happened because he will have a fit.

The Ashen Wolves decide to stay in Abyss while the others return to the surface. The other Black Eagles, Blue Lions and Golden Deer get along with the Ashen Wolves, and Bernie, Marianne and Constance begin to relate.

Into Darkness:

The annual Battle of the Eagles and Lions is delayed after the Flame Emperor's forces stage an attack on the Holy Mausoleum, where Seiros' remains are allegedly stored. But they only manage to uncover a Relic called the Sword of the Creator, which was said to be made of the bones of a goddess. In the aftermath, it seems Byleth is able to activate its power when in grasp. So Rhea entrusts it to them. Byleth also eventually learns Sothis is the name of the goddess of Fódlan, which must mean the girl that has been residing in their head all this time must be it.