Titan

s (巨人) are the false primary antagonists in the Attack on Titan series. They are a race of giant humanoids that were thought to have first appeared 107 years ago and rapidly exterminated humanity to the point of near-extinction. In reality, the Titans are transformed Eldians that have roamed the earth for nearly 2,000 years since the days of Ymir Fritz.

Appearance
Titans greatly resemble nude human beings. They are bipedal creatures with the same number and arrangement of limbs and features one would expect in human beings. They are all deformed by human standards to a greater or lesser degree, ranging from minor abnormalities in proportions (enlarged head, small limbs, etc.) to apparently lacking skin and subcutaneous tissues, although they do not bleed from such deformities. The vast majority of Titans have a masculine body shape, although all of them lack reproductive organs.

Titans, in many cases, have exceptionally wide mouths with an enormous number of small, square teeth. Although some only possess canines, a majority of Titans lack them. In all likelihood, they have and use incisors for their primary activity: eating humans. Titans do not possess a complete or functioning digestive tract, and merely have a stomach-like cavity that eventually fills up with what they swallow. After consuming a certain amount, they are forced to regurgitate and empty out the cavity before they can eat more humans.

Behavior
Titans are subconsciously compelled to seek out and devour humans for a chance that they might possess the power of the Titans, who are able to change between human form and Titan form at will. If a Titan consumes a human with this power, said Titan will be able to return to human form with the power of the Titans. They do not derive any real sustenance from humans, as many of them did not taste human flesh for nearly a century after the Walls went up. This did not affect their activity or numbers. It should also be noted that once a Titan has filled up its stomach-like organ with dead humans, it regurgitates them in a giant ball and continues eating more as soon as possible.

Most Titans have no intelligence at all and are simply mindless beasts, easy to trick, distract, or deceive. However, some Titans, mostly humans with the power of the Titans, possess a vast level of intelligence comparable to or exceeding an experienced and cunning human. For example, the Female Titan and, to a lesser extent, the Colossus Titan display acute intelligence, a trait not found in an ordinary Titan. A Titan encountered by Ilse Langnar possessed enough intelligence to speak and bow before her, calling her "Lady Ymir".

However, although most Titans show no visible or audible form of communication, they are apparently aware of - and able to deduce hostile intent from - other Titans. Titans do possess the ability to roar, but do not appear to possess the mental capacity necessary to speak human languages, with only rare exceptions.

Pure Titans can be controlled and commanded by the power of the Founding Titan to be used as weapons of mass destruction as they had been in ancient times. However, without the Founding Titan, they wander aimlessly following no orders.

Physiology
The Titans' body structure and power source are very mysterious and they apparently violate several known laws of science, seemingly capable of spontaneously generating both energy and mass. Their extremely high level of activity and body temperature indicates the need for a massive intake of energy to fuel them, yet they apparently never need to eat at all. They possess vocal organs and are able to emit simple sounds like roars and screams, yet they apparently do not need to breathe. They do seem to become less active at night or if deprived of sunlight, and so it may be possible they draw their primary source of energy from the sun. Individual Titans seem to possess varying levels of stamina once deprived of sunlight; during experimentation, the captured Titan "Sonny" became docile and nearly comatose after only an hour's deprivation, while fellow captive "Bean" maintained a high level of activity three hours after last seeing sunlight.

However, after the invasion of Wall Rose, Titans were seen moving in the dead of night when they should be inactive, traits they normally do not express. It has been theorized by Hange Zoë that since Titans receive sustenance from sunlight, moonlight would also be sufficient enough, due to the moon being reflected sunlight. She reasons that this is why there were so many Titans storming Utgard Castle during said invasion, as it is believed that many of those Titans had been freshly created from Ragako.

Titans' bodies also seem unusually light for such large creatures - a severed arm is described as weighing almost nothing, and they are able to move at high speeds despite their size. Due to their size, Titans possess enormous strength and when combined with this lightness, they can put on amazing bursts of speed and agility.

In addition to their size, speed, strength, and large numbers, Titans also possess incredible regenerative abilities - the only known sure-fire way to kill them is by slicing out the nape of the back of the neck. They regenerate lost and damaged body parts within seconds to minutes, including severed heads (unless the nape is severed with the head). It should be noted that the vulnerable area is where the real human body would be for transformed Titans, as proven by Eren Yeager. When struck at this site, the human controlling the Titan (or rather, what remains of them) is decapitated, killing both. After death, Titan corpses rapidly evaporate to skeletal remains, then to nothing at all.

How Titans react to pain stimuli varies from one to another. Many Titans will completely ignore injuries which would be agonizingly painful to a human, such as losing limbs, being impaled through the heart, or having their eyes gouged out. In combat, some Titans will completely ignore armed humans who are attacking them, and simply proceed to attempt to eat whichever human is closest to them. Others seem vaguely aware of humans who are attacking them, and if injured will have a reaction that might be pain but more accurately seems like simple annoyance. On the other hand, some seem to react in pain and shout when they are injured.

Creation
In the aftermath of the destruction of Ragako, the true nature of the Titans is discovered. The investigation performed by Hange Zoë reveals that the villagers had been transformed into Titans by some unknown means, as a captured Titan is discovered to have once been Connie Springer's mother. Examination of test subjects show that no human body remains within the nape, but Hange speculates that the spinal cord operates as an organ separate from the main Titan body. As such, it is concluded that most Titans have completely absorbed the human within, leaving only the central nervous system intact as the means of controlling the Titan body. The method used to slay Titans is revealed to sever the upper vertebrate of the human "pilot" (or what remains of them), killing them via decapitation.

Hange theorizes that Titans can absorb abilities from their victims, allowing an ordinary Titan to regain human form by devouring a Titan shifter. This was discovered when Ymir, then a regular Titan, devoured the young Titan shifter Marcel and regained human form. Hange theorizes that not only can Titan shifting be transferred this way, but other unique traits such as Eren's Coordinate ability could be transferred in the same fashion. This is now confirmed as a fact by Rod Reiss and now it is known that memories will also be transferred to the one who ate the shifter, along with any powers they may possess. It is also possible that beliefs can be passed down if the person ate somebody of their bloodline, as the Reiss who possessed the Coordinate would be bound to the will of their ancestor, the First King, making them not want to exterminate the Titans, and never revealing to anybody the reasons why.

It is revealed that the injection that Grisha Yeager gave his son Eren was able to turn Eren into a normal Titan, allowing Eren to eat Grisha. Grisha, being a Titan shifter, transformed Eren into a Titan shifter and passed down the Coordinate and Frieda Reiss' memories at the cost of Grisha's life. The Reiss family has done this method for years, having one Reiss transform into a Titan via injection and eat the holder of the Coordinate, gaining Titan powers, memories of the lost world, and the Coordinate.

The serum in the injection is, most probably, the method through which most, if not all, Titans were created, though its way of administration can vary, as evidenced by the Beast Titan's inoculation of Ragako, implying that the agent can be spread through a multitude of mediums other than just a serum. Rod Reiss also gives insight into the vast multitude of physical structures and frames the Titans manifest, implying that it is actually possible for a serum to induce a certain kind of Titan, and in Rod's case, an immense Titan twice as big as the Colossus Titan. According to Hange, the serum is derived from human spinal fluid, but contains elements beyond the capability of their current science to analyse. The serum is also difficult to study because it begins to vaporize immediately upon contact with air.

History
While the true nature of the Titans remains a mystery, their origins have been documented in the legends of the Eldian people. Over 1,800 years ago, it is said that Ymir Fritz, an ancient monarch of the royal Fritz family, discovered the "source of all organic material" and gained the power of the Titans. Ymir became the first known Titan, and when she died thirteen years later, her "soul" was split, being passed down unto nine Titan inheritors. After the death of Ymir, the nine Titans made use of the Titans and their own powers to conquer the peoples of the world, including the nation of Marley. Upon conquering the world, the nine Titans established the empire of Eldia, led by the Fritz family who held Ymir's Founding Titan. Afterwards, the other eight Titan clans began to fight amongst each other, though throughout the generations the Fritz family maintained order with the Founding Titan.

However, after 1,700 years, the 145th Fritz King inherited the Founding Titan and chose to abandon the conflicts of the mainland. In his absence, the Marleyans stole seven of the nine Titans and waged war against the Eldians, and the Great Titan War began in which the Titans were used by the Marleyans to wipe out the nation of Eldia. The King and his family fled to the island of Paradis, where he used Colossus Titans to construct three Walls around his territory. In years after, Marley would send undesirable citizens to Paradis as mindless Titans, doomed to wander the island in search of food.

Types of Titans
Titans are classified according to their size and abilities. The following is a list of various known Titans so far.

Trivia

 * Some Titans are modeled after friends and acquaintances of Hajime Isayama. Sometimes, he will even take requests.
 * In the August 2016 Issue of Bessatsu Shonen Magazine, Isayama was asked of what is it like to come out of a Titan's body. He stated, "Just think that it’s like coming out from a sauna."
 * While many Titans have a masculine appearance, some Titans seen have had feminine facial features although retained a masculine body shape.

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