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Grisha Jaeger is a character from the manga series Shingeki no Kyojin better known as Attack on Titan. After being thought by Eren dissappeared since he inject him with an unidentified serum that bestow him power to transform into a powerful titan, he turned out revealed as a major posthumous antagonist whom killed Frieda, another Titan Shifter in the past to gain her ultimate power that later fell onto Eren's hands along with his Titan Shifting powers, at the cost of his own life.
Grisha was a doctor who lived in Shiganshina district and a Titan Shifter. He was the father of Eren Jaeger and Carla's husband. Grisha was known for saving hundreds of lives from a plague that hit mankind. He used to keep everyone away from his basement. The Jaeger family lived peacefully with the adoptive daughter Mikasa Ackerman until one day, the Colossal Titan destroyed the gate. After the fall of Wall Maria, a tearful Dr. Yeager injects a serum into Eren's left arm, which Eren believes is responsible for giving him the ability to shift into a Titan. Dr. Yeager tells Eren that the serum will cause memory loss and gives him the key to the basement, saying that all of the answers can be found there.It is later revealed by Rod Reiss that Grisha, in his Titan form, entered the Reiss family chapel, where they were gathered. In the chapel, he appeared with a frightened expression as he confronted them, with Frieda protecting them. He used a knife to stab his hand and subsequently transformed, and Frieda as well by biting her hand. Rod reveals that Grisha was after Frieda's Titan power, and that Frieda's Titan was had an "invincible power", but she lost due to lack of experience. Grisha ate Frieda, stealing her Titan powers, and brutally slaughtered the remaining Reiss family. Among the deceased were Rod's fourteen-year-old son Dirk and twelve-year-old son Abel, both of whom he crushed with his hand. He also stomped on ten-year-old Florian, who died with his mother, and squeezed to death Rod's eldest son Ulklin. He destroyed the chapel and Rod was the only one who managed to escape.
Grisha was later killed and eaten by his son Eren after the latter turned into a mindless titan by an injection into his arm that caused him a memory loss.