Eldia

Erudia (エルディア) is the nation occupied by the Subjects of Ymir (ユミルの民), often referred to as Eldians. The people of Eldia are said to be the only humans capable of turning into Titans, a trait which was despised in them in later history. In ancient history they dominated the world, until a century ago when the Great Titan War isolated many of their people onto the island of Paradis within the walls where the 145th Fritz king had fled.

History
Around 2000 years before the battle of Trost District, the Fritz family came into power as the royal bloodline of humanity. Over a century later, a girl by the name of Ymir Fritz made a deal with the "Devil of the Earth" and was made into the first of all Titans. Her power as the Progenitor Titan brought great prosperity to her people, and when she died her "soul" was divided between Nine Titans, the chief among them inheriting her role as the Progenitor Titan. With their Titan powers, the nine Titans waged war against Marley, an empire of the early world, and came to rule their continent.

After conquering the Marleyan people, the Subjects of Ymir established a new nation by the name of Eldia. The Eldians continued to subjugate and slaughter the Marleyans, committing eugenic rape against their people in order to spread their own numbers. Eventually, the eight Titan clans subservient to the Fritz family began to fight amongst each other, though the power of the Progenitor Titan always maintained order throughout the lands of Eldia.

After 1,700 years, the Progenitor Titan came into the possession of the 145th King of the Fritz family. At this time, the people of Marley managed to steal seven of the nine Great Titans, drastically turning the tide of their conflict. This marked the beginning of the Great Titan War, in which Eldia lost its territory on the continental mainland. The 145th Fritz King chose to abandon the conflict in favor of isolating the remainder of the royal family and their followers on the island of Paradis, Eldia's last domain of undisputed territory. On the island of Paradis, the King used the Progenitor Titan to cause Colossus Titans to form three concentric walls around their territory: Maria, Rose, and Sheena. Afterwards, the 145th Fritz King, now known as the First Reiss King, used the Progenitor Titan once more to erase the Eldians' memory of the Great Titan War and all of history before the raising of the walls. For the next century, the Eldians of Paradis lived on in peace, unaware of their past conflicts or their history as the Subjects of Ymir.

The Eldians who did not flee overseas to Paradis were in the end conquered by the Marleyans, but were spared. These Eldians became low-class citizens, forced to reside within designated ghettos separate from the Marleyan population. Any Eldians accused of committing wrongdoing against the Marleyans were turned into mindless Titans, doomed to wander the lands of Paradis searching for human food. Some Eldians such as Grisha Yeager, however, met together in secret, plotting to venture to Paradis and retrieve the Progenitor Titan in order to bring back the nation of Eldia.

Ilse's Notebook
In the year 848, Ilse Langnar of the Survey Corps became the last surviving soldier of the left flank of the 2nd brigade during the 34th Expedition, lost in Titan territory within Wall Maria. With her vertical maneuvering equipment broken and horse missing, she chose to record her experiences as she made her way north toward Wall Rose. During her journey, she is caught by a Titan who forces her back against a tree but refrains from eating her. The Titan speaks to her, first believing her to be "a subject of Ymir" before mistaking her for "Lady Ymir" herself. Ilse attempts to communicate with the Titan while taking notes, asking what it is, where it comes from, and, after losing her composure, furiously asks why they eat humans. The Titan only responds with pained moaning and later starts ripping off its cheeks when Ilse screams at it. When she attempts to flee, the Titan catches her and crushes her head between its jaws (while taking notes until her last breath), but does not consume her body. Her notebook and remains were discovered a year later by Hange Zoë and Levi Ackerman.

Return to Shiganshina arc
Upon finally reaching the basement in the Yeager family household in Shiganshina, the Survey Corps discovers three of Grisha Yeager's books, describing all his knowledge of the history of Eldia and his own experiences in joining the Eldian resistance in Marley.