Name: Mithos Yggdrasill
Age:4000 years old
Race: Angel
Weapon: Sword
Looks: Blond hair, white clothes and pink angel wings....
Story: According to legend, Mithos and his three companions stopped the Ancient Kharlan War and restored peace to the world. Early on, it is believed that they had sealed away the Desians. Later, however, the war is discovered to have been between Sylvarant and Tethe'alla - completely irrelevant to the Desians. This group of mythical heroes was composed of three half-elves and one human. Mithos's full name is not revealed until extremely late in the game, along with the identities of the heroes: Kratos Aurion, Mithos's sister Martel, and Yuan. They would later be referred to as the Four Seraphim, the leaders of Cruxis. The whole group, aside from Martel, who was slain in the war, is over 4,000 years old (although Martel's soul still "lives" in a vegetable-like state).
During the War, the companions went through many great hardships due to discrimination against half-elves, fueled by both humans and elves. Because of this discrimination, Mithos and Martel were shunned from their home of Heimdall, and forced to live on their own. During this time, Mithos was being trained as a swordsman and a mage by Kratos. He would eventually go on to become the great hero of legend by making pacts with each of the Summon Spirits single-handedly (although he had Kratos make the pact with the King of Summon Spirits, Origin, in his place). Mithos then had Origin create the near-omnipotent Eternal Sword, which he used to split the world in two (to create the parallel worlds of Tethe'alla and Sylvarant) in order to prevent more magitechnology from being created. The Ancient Kharlan War was caused by magitechnology, which consumes vast amounts of mana; by splitting the world in two halves and having them vie for the small amount of mana, Mithos effectively stopped the creation of magitechnology and a second cataclysmic global war. Part of the pact with Origin was a promise that he would restore the Great Seed to the world so that it could grow again; this would restore mana to the land. Instead, Mithos took it to Derris-Kharlan in order to revive and protect his dead sister, thereby breaking his pact with the Summon Spirits.
Mithos had strong ideals about peace and unity, but his sister's death deepened his hatred for humanity and made him lose track of whether the world, or her life, was more important to him. He took her final words to heart, her wish for a world without discrimination, which he interpreted as a wish to end the persecution of those who were half human and half elf (what Martel truly wanted was an end to discrimination between all the different races, as stated by Yuan). Mithos' ideals then became twisted; he came to the conclusion that the only way for discrimination to end was, in his own words:
"By using the Exspheres to eliminate the different bloods that flow within elves and humans, everyone will become the same lifeless beings. Discrimination will vanish. That is the grand age I strive for."
"People fear and hate what is not normal. They are scared of those that are different. Then the solution is for everyone to become the same."
To this end, he began mutating half-elves, using a superior form of Exsphere known as Cruxis Crystals. These Cruxis Crystals turned their subjects into near-immortal angel-like entities at the cost of the things that made them human. Even if the body of an angel was destroyed, the Exsphere would also need to be destroyed as well for them to truly die; it was possible to live on in a Cruxis Crystal even after the body of its subject had been destroyed. These "angels" are often referred to as "lifeless beings".
Mithos also founded the Church of Martel, and therefore became, in a way, the absolute ruler of the two worlds. In order to resurrect Martel, Mithos would need to find a subject whose mana signature was nearly identical to Martel's. Acting as a supreme lord of angels, he manipulated the bloodlines of the citizens of the two worlds for over 4000 years in order to create this vessel. Mithos declared Martel a goddess and became remembered as a hero.