Frieda Reiss

Frieda Reiss is Rod's eldest daughter and Historia's half-sister. She has long black hair and bears such a striking resemblance to Historia that Eren once mistook her for Historia. She was well-liked by the people for her bright and unpretentious personality.

At the age of 15, she injected herself with the Titan serum passed down in the Reiss family, transforming into a Titan. She devoured her uncle Uri, the previous inheritor, and inherited the "Power of the Titans" and the "Memories of the World" he held. However, in the year 845, when Wall Maria was breached, she was defeated in battle by Eren's father, Grisha, and was eaten by him, resulting in her death.

Before her true identity was revealed, she was a mysterious presence that would suddenly flash back in Eren's memories or appear in Historia's dreams. The memories of Frieda that Eren possesses were brought to him through Grisha, who had devoured the Founding Titan.

She had the ability to alter people's memories, a power passed down in the Reiss family. She had been closely watching over Historia since she was a child, but after meeting her, she used her power to seal Historia's memories, preventing her from recognizing Frieda's existence for many years. To Historia, who grew up feeling isolated, Frieda was the only relative who showed her love.

After inheriting the Founding Titan, there are depictions of her being tormented by the "Power of the Titans" and the "Memories of the World." Before inheriting, she intended to resist like her uncle, saying she wouldn't lose to the "ghosts of the ancestors," but ultimately, she was controlled by the "Vow of Renunciation of War" made by Karl Fritz and chose the "path of self-destruction" like the previous inheritors of the Reiss family.