Source of All Living Matter

Nearly two millennia before the story begins, a fleeing slave girl named Ymir Fritz touches an anomaly beneath a colossal tree and emerges as the first Titan. The entity responsible has no true name; "source of all living matter" is a tentative label, and across history it has been called the Devil of All Earth, God, and, in Gabi Braun's later description, a "shining centipede." Eren Kruger, recounting the competing legends to Grisha Yeager, admits that every explanation of Ymir's power is ambiguous and keeps shifting with the telling. Zeke Yeager frames its deeper significance in his account of life's beginning: among countless self-assembling masses appearing and vanishing in the primordial world, a single one endured, and that survivor became what we call life.

The creature resembles a glowing, segmentless arthropod, its limbs flowing seamlessly from its body, with a cluster of feelers where a face should be and no visible eyes or mouth. Its scale is elastic, roughly a meter long when it joined with Ymir yet gargantuan when it later erupts from Eren Yeager's Founding Titan.

Whether or not it truly seeded life on Earth, the anomaly demonstrably warps living things around it. The ancient tree above its resting place dwarfed every tree nearby. Contact with Ymir created the Power of the Titans outright and wove the living and dead consciousness of the Eldian race together through the paths. Zeke speculates the power's defining traits, colossal near-indestructible bodies and an escape from death, crystallized from Ymir's own terror of dying.

Though usually inert, it moves with startling purpose under threat. It stretched its limbs toward Ymir as she approached, and during the Battle of Heaven and Earth it twice surges from the stump of Eren's neck to reconnect with his severed head, preserving his life after Gabi's rifle shot decapitates him. Denied that reunion a second time, it turns violent, hurling itself at the Armored Titan.

As the wellspring of the power itself, it wields the same abilities as the giants descended from it. When it is cut away from Eren's Founding Titan during the fighting at Fort Salta, it vents a gas functionally identical to Zeke's weaponized spinal fluid, involuntarily transforming every nearby Subject of Ymir into Titans that rush to shield it.

Only two beings ever host the anomaly. Ymir Fritz is its first vessel, gaining the Founding Titan's immense form the moment they touch. Eren Yeager becomes the second, sustained by it after his decapitation at Shiganshina, when contact with Zeke sends the brothers into the paths, where Eren sees firsthand how Ymir's power began.

In the final battle it takes the stage as an enemy in its own right. After Jean Kirstein's explosives sever the Founding Titan's head, the now-colossal creature writhes toward the severed skull until Reiner Braun's Armored Titan pins it and Armin Arlert's Colossus transformation engulfs them both. It survives the blast, unleashes its Titanizing gas over Fort Salta, and is defended by the transformed Eldians while Annie Leonhart and Pieck Finger join Reiner against it. Only Eren's death ends it: the moment he dies, the creature vanishes and the Power of the Titans disappears with it. Its design echoes Hallucigenia, a bizarre worm of the Cambrian seas, and the final chapter closes on a tree over Eren's grave grown to mirror the one where Ymir first met the entity.