|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.|
|— Mr. Jaeger tells his son of Ymir's tale|
The Devil of All Earth (大地の悪魔 Daichi no Akuma?) is a figure of Eldian mythology who made a deal with Ymir Fritz, granting her the power of the Titans. The Subjects of Ymir are called the "spawn of the Devil" (悪魔の末裔 Akuma no Matsuei?) because of this belief.
The world was convinced that the Devil of All Earth was real, slain by the Marleyan hero Helos during the Great Titan War, until Willy Tybur revealed that the story of Helos is mere propaganda. Eren Kruger suspected that Ymir's deal with the Devil was fabricated by the enemies of her people, although the tale is told in an Eldian book as well.
In all illustrations depicting the Devil, it is shown as a large, crouching figure with a menacing smile. In the book Frieda Reiss reads to Historia, the Devil is covered in a large cloak and hood, whereas in the book Grisha's father reads to Grisha, its head is exposed, revealing two goat-like horns and a long tail. It also appears with sharp claws, large muscles, and pointed ears.
In a bronze statue in Liberio depicting Helos slaying the Devil, he takes on a much less demonic appearance, becoming more Titan-like with a thick beard and a full head of hair, lacking visible horns.
Over 1,800 years before the Fall of Wall Maria, a girl by the name of Ymir Fritz is said to have met with the Devil, and the two made a deal. It is unknown what Ymir offered the Devil, but in return it granted her immense power, turning her into the first of all Titans. Eren Kruger later claimed to Grisha Jaeger that this myth was open to interpretation and that there was no absolute truth in the world, also giving the option that she discovered the source of all living matter, where she gained the power of the Titans.
At the time when Historia Reiss, a direct descendant of Ymir Fritz, was growing up on her family's farm in Wall Sina, her half-sister Frieda Reiss visited her frequently, teaching her important life lessons such as reading and writing. Occasionally, Frieda would teach Historia the story of Ymir and the Devil; however, in this story, the girl is named "Christa" instead of Ymir. Frieda instructed Historia to be a loving and beloved girl as "Christa" was.
In the year 850, when the Scout Regiment discover 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 deal with the Devil by his father and Eren Kruger.