Power of the Titans

Ymir Fritz acquires the power roughly two millennia before the story's close and becomes the first Titan. Thirteen years later she dies, and since no successor may outlast the Founder, everyone who gains the power afterward inherits her ceiling. This limit, the Curse of Ymir, caps a holder's remaining lifespan at thirteen years from acquisition, the final stretch marked by a weakening body; Uri Reiss, Tom Ksaver, and Eren Kruger all sickened and seemed to age dramatically in their last year. The whole system ends only when Ymir elects to relinquish the power itself, at which moment every surviving Titan reverts to an ordinary human.

Transformation demands an injury that draws blood, frequently self-inflicted, paired with a defined goal held in mind at the moment of harm; a wound dealt by someone else works equally well. Energy erupts, a giant body forms, and hot steam pours off it, with the human riding in the nape as the center of control, flesh partly fused to the Titan's, most often below the eyes. First transformations frequently spin out of control, endangering friend and enemy alike. Driving a form to exhaustion ejects its user semi-conscious or worse, while a fresh form can be left at will, even partially. Dark markings ring the eyes afterward, fading over minutes or hours depending on strain and skill. Overuse carries a graver cost: rapid repeated transformations shrink the Titan, weaken control, and edge the user toward permanent absorption into the flesh. The Cart Titan sidesteps this economy through sheer endurance, its holder Pieck once remaining transformed for two months straight. Transformation also wrecks the immediate surroundings, and the Colossus Titan alone can swell that release into something resembling a nuclear blast, as Bertolt Hoover showed at Shiganshina and Armin Arlert repeated against the fleet at Liberio.

Regeneration keeps holders alive through injuries up to partial or full decapitation, so long as the will to live holds, though healing severe damage can block transformation for a while, and healing can even be postponed deliberately, a trick Eren used to pose as a wounded soldier in Marley and Reiner used while embedded on Paradis. Killing a holder outright requires cutting the brain off from the rest of the body, and transferring the mind into the nervous system can cheat even that briefly. Memories travel to new inheritors through the paths, surfacing more readily through touch and flowing far more strongly along blood lines; the Reiss and Tybur houses could see generations deep, while unrelated inheritors like Ymir and Armin received nearly nothing at first. The Attack Titan stands alone in receiving memories from inheritors yet to come, which let Kruger speak names of people not yet born and let Eren reshape the past through his father. Hardening, finally, is available to all nine with training, from reinforced fists to the crystal cocoons of the Female and War Hammer Titans, and a specialized serum granted it to Eren's Attack Titan instantly.

Transfer obeys one rule: a Titan that devours a holder, or simply bites through the spine and swallows the spinal fluid where the power lives, claims it and regains human form. Titan serums are that same spinal fluid, notoriously hard to study because it evaporates on contact with air. If a holder dies without being eaten, the power resurfaces in a newborn Subject of Ymir somewhere in the world, indifferent to distance or kinship. The fluid's source also leaves fingerprints: Falco Grice, turned by fluid from Zeke Yeager, produced a Jaw Titan with the avian traits of a Beast, and Annie Leonhart's Female Titan underwent extensive trait manipulation the same way. Royal blood unlocks the deepest tier, allowing Zeke to create Pure Titans with a scream and steer them even at night, while full command of the Founding Titan belongs only to royal inheritors or to outsiders touching a royal-blooded Titan. The Ackerman clan echoes the power in a different register, drawing the accumulated combat experience of every previous Ackerman through the paths without ever transforming at all.