Titan

A Titan looks like an enormous unclothed human, usually walking upright though a rare few move on four limbs. The proportions are always wrong somewhere: an oversized skull, stunted arms, a distorted torso. Mouths stretch unnaturally wide, filled in most cases with rows of uniformly flat teeth, though some carry entirely sharp ones instead. Nearly every Titan displays a masculine build and none possess reproductive organs; women who transform keep little that is feminine about the body. Ordinary specimens, the Pure Titans, run from 2 to 15 meters in height, those showing strange behavior or flickers of intelligence are classed as Abnormals, and the Nine Titans, fragments of Ymir Fritz's original power, answer to human pilots who keep their own minds and bodies.

Titan biology defies known science, conjuring energy and mass from nothing; the material is said to arrive through invisible paths that cross beyond physical space, all converging on one point, the coordinate that is the Founding Titan. Their bodies are strangely light for their bulk, hot, and hyperactive, yet they never need food, never need to breathe, and take their working energy from the sun. Darkness shuts them down at varying speeds: the captive Sonny went nearly comatose within an hour of losing the light, while fellow prisoner Bean stayed lively for three. The Nine ignore this limit, as do Titans directed by a royal-blooded Beast Titan or by the Founder itself.

Regeneration makes them close to unkillable. Lost limbs and even severed heads grow back in seconds to minutes, and the one dependable kill is a deep cut across the nape, a strip about a meter long and a hand's width across that houses the creature's true nervous center; in a Pure Titan that spot holds an absorbed human spine, in the Nine an entire human body. Dead Titans steam away to bone and then to nothing at all. Pain response varies wildly between individuals, and people wielding the power of the Titans feel nothing when their Titan flesh is damaged. Their drive is singular: they hunt and devour humans while ignoring every other living thing, gaining no nourishment from the act, swallowing victims into a dead-end stomach cavity that gets vomited out once it fills. Most are mindless and simple to trick, but the Nine carry full human intellect, and rare Abnormals, Connie Springer's mother and the Titan that met Ilse Langnar among them, retain fragments of thought and speech.

New Titans come only from the Subjects of Ymir, the people distantly descended from Ymir Fritz and linked through the paths. An injection of Titan spinal fluid transforms one almost instantly, a method Marley long exploited. The Founding Titan can transform Subjects directly, which is how Karl Fritz produced the Colossus Titans locked inside the Walls, and Zeke Yeager, owing to his royal blood, mimics that power by screaming at victims dosed with his spinal fluid. The resulting Titan often resembles the human it was made from.

Roughly two thousand years before the story, a slave girl named Ymir flees her Eldian masters and falls into a water-filled hollow beneath a great tree, where a creature resembling a spine fuses with her and makes her the first Titan. She serves King Fritz, bears him three daughters, and when she dies the king forces the girls to eat her body so the power will not be lost. Split among them, the ability divides further over generations into nine distinct Titans, and with those weapons Eldia conquers Marley and builds an empire, the Fritz family using the Founding Titan to hold the feuding noble houses in check while Pure Titans serve as instruments of war.

Some 1,700 years into that era, Karl Fritz inherits the Founder and walks away from the mainland's conflicts. The Great Titan War breaks out in the vacuum, and the chaos lets the Marleyans rise and seize the continent. The king withdraws to Paradis Island with many of his people and rings his territory with three Walls built from countless Colossus Titans. In the decades after, Marley transforms condemned Subjects of Ymir and abandons them to roam the island beyond the barriers. Behind those Walls, generations grow up taught that the giants simply appeared 107 years before the year 850 and devoured mankind nearly to extinction. The species ends when Eren Yeager dies and Ymir chooses at last to relinquish her power, returning every Titan to human form and erasing the race from the world.