Grisha Yeager

Grisha Yeager was a physician who served the people within the Walls, saving countless lives during a devastating epidemic through advanced medical knowledge he had brought from the world beyond the Walls. His healing deeds, which included curing the parents of Carla and the wife of Hannes, eventually won Carla's heart, and the two married and had two sons, Eren and Zeke. During a house call, he also took in Mikasa after she was left orphaned. Grisha was not a native of the Walled world; he was discovered by the Survey Corps approximately in the year 832 during an expedition beyond the Walls, with almost no memories other than his name and profession. He was guided into understanding life within the Walls by Ksaver. Carrying a profound secret concerning the Titans, he concealed it in the basement of his home and entrusted the key to Eren, urging him to seek it out someday. After Wall Maria fell, Grisha rushed to Eren's side, injected him with a mysterious serum, and subsequently vanished. Investigations later revealed that he had engaged Frieda Reiss in battle at a chapel on the Reiss family estate, ultimately devouring her and seizing the power of the Founding Titan.