Born during Quirks' emergence as Zen Shigaraki, one of twin brothers, his unnamed sex-worker mother died post-childbirth. Even in utero, he absorbed most nutrients, leaving twin Yoichi frail. Immediately upon birth, he stole his mother's Quirk with his innate theft ability, establishing his parasitic nature from infancy. Raised in societal chaos, he adopted a survivalist worldview, treating existence as his property. He indiscriminately seized food, resources, and Quirks, accumulating power. Comic books depicting a "Demon Lord" shaped his ambition to become a Symbol of Evil. By gifting Quirks to the powerless in exchange for loyalty, he built a criminal empire under the guise of restoring order. His bond with Yoichi remained complex: viewing his brother as property yet granting him a stockpiling Quirk for strength. Unaware of Yoichi's latent transfer ability, their merged powers created One For All—the sole Quirk he couldn’t steal. When Yoichi joined a resistance, All For One killed him, sparking a century-long fixation on reclaiming "his first possession." Physically, he presented as a tall, white-haired man with red eyes, often in formal suits. After battling All Might, severe facial scarring left him blind, reliant on life-support and a skull-like mask. Infrared and vibration-sensing Quirks aided navigation. During a later clash with pro heroes, he activated a replicated Rewind Quirk, temporarily reverting to his prime. Sustained damage accelerated the Quirk’s effect, regressing him through child, infant, and fetal stages into an egg cell before vanishing. He mentored Tomura Shigaraki (born Tenko Shimura) as a successor. Rescuing Tomura from childhood trauma, he manipulated the boy’s hatred and provided preserved family hands as psychological anchors. His apparent affection was calculated; he intended Tomura as a vessel for his consciousness and Quirk, executing a body hijack during the Paranormal Liberation War. His Quirk enabled theft and transfer of others’ abilities via touch. Key stolen powers included "Search" for target tracking, "Warping" for teleportation, "Rivet Stab" for tendril assaults, and "Forced Quirk Activation" to weaponize enemies’ abilities. He combined Quirks tactically—layering strength enhancers against All Might or using "Impact Recoil" to reflect damage. "Life Force" extended his lifespan, while "Bloodcurdle" induced paralysis. Personality-wise, he exhibited megalomania and detachment, treating individuals as disposable tools. He maintained pragmatic calm even in defeat, employing psychological warfare against foes. Though courteous to subordinates, he discarded them post-utility. His sole acknowledged connection was Yoichi, addressed in internal monologues as though seeking completion. In his final confrontation, he attempted to steal One For All from Izuku Midoriya through Tomura’s body. Thwarted by the vestiges of past users, the Rewind Quirk’s overuse erased his physical form. His consciousness endured as a vestige within Tomura.