|One thousand, eight hundred and twenty years ago, our ancestor Ymir Fritz made a contract with the Devil of All Earth and obtained the Power of the Titans.|
|— Grisha's father tells his son of Ymir's tale|
Ymir Fritz (ユミル・フリッツ Yumiru Furittsu?) was the progenitor of the Eldians. When she was a young girl, she awakened the power of the Titans and became the first Titan, the Founding Titan. After she died, her spirit was split into the Nine Titans.
Ymir Fritz had long, thick, light-colored hair and was often shown holding an apple. She was usually depicted in illustrations wearing a flowing dress with loose bell sleeves and a tie around the waist, along with a pair of basic flat shoes.
In posthumous illustrations, Ymir's Titan form is highly romanticized with more human features.
Being a subject of ancient history, little is known about who Ymir truly was as a person. When reading about her story to Historia, Freida describes her as a kind girl who is always thinking of others, as well as lady-like. Additionally, Eldians such as Grisha Jaeger speak of Ymir with great reverence, praising her accomplishments for their people. On the other hand, the Marleyan propaganda maintains that Ymir was a pawn of the Devil, whom she had made a deal with and caused her and all her subjects to be despised by much of the world.
Over 1,820 years ago, Ymir Fritz somehow gained the Power of the Titans. According to Kruger, this was done when she came into contact with the "source of all living matter" as a young girl. With this power, Ymir became the progenitor of all Titans. The power of her Titan, the Founding Titan, was the coordinating point linking unseen "paths" which united the minds of her people, the Subjects of Ymir. What she accomplished with her powers is unknown, but after 13 years Ymir met her death, and her "soul" was split between nine successors who went on to build the Eldian Empire. Afterwards, all inheritors of her power would be doomed to die after 13 years as she did, in a phenomenon that would later be known as "The Curse of Ymir." No Titan would possess more power than Ymir had possessed in life.
Some time after her death, Ymir's existence was hailed as a god-given miracle. Many would claim that as the Founding Titan, she used her Titan power to cultivate barren lands, build roads across the lands, and raise bridges through the mountains of the world, though these claims could never be supported. On the other hand, after the fall of the Eldian Empire in the Great Titan War, the new Marley government would spread slanderous legends that Ymir's power was derived from the "Devil of All Earth."
In her childhood, Historia used to read about the story of Ymir with Frieda; however, in this story Ymir is named "Christa." When Historia asked Frieda what is it like to be "ladylike," Frieda replied to be like "Christa" from the story.
Some years later, when the Scout Regiment discovers Grisha Jaeger's basement, they find three journals. Within Grisha's writings, he recounts his childhood when he was told the story of Ymir and her people by his father. Grisha writes of joining the Restorationists in the nation of Marley several years afterward, learning of the supposed great accomplishments achieved in Ymir's time. Together with the resistance, Grisha declares that they must venture to Paradis Island, where Ymir's descendants had fled eighty years ago, in order to retrieve the Founding Titan and bring back the nation of Eldia.
Ymir was the very first Titan and the only one to ever possess the complete power of the Titans; all who come after her merely possess fragments of her power. It is said that nobody can surpass Ymir and that because Ymir died 13 years after awakening her powers, no one is allowed to live beyond that; this phenomenon is known as the "Curse of Ymir."
- Ymir/"Christa" is on the cover of the book Historia Reiss used to read when she was a child.
- Ymir can be seen at the beginning of Season 2's Ending Theme, Yuugure no Tori, and briefly in Season 3's second Opening Theme, Shoukei to Shikabane no Michi.