Titan Shifting, Regeneration
Titan Shifters are humans in possession of the "Titan's power" (巨人の力 Kyojin no Chikara?), which allows them to transform into Titans. They are able to direct the powers and abilities of a Titan with purpose, and unlike regular Titans, retain their human intelligence.
To transform, they must suffer an injury that draws blood (often self-inflicted), as shown when Eren Yeager bit his hand to protect Mikasa Ackerman and Armin Arlert, and when Annie Leonhart stabbed her finger with a blade from her ring, while having a solid goal or belief in mind at the moment of injury. However, being injured by another person is also sufficient, such as when Mikasa seriously wounded Reiner and Bertolt. After their transformation, their human bodies appear to be in the Titan's nape of the neck, where they control their Titan bodies. Their human bodies are also merged with the Titan's flesh inside, making it hard for them to move.
If a shifter's Titan form is pushed to its limit, its human form will emerge from the nape of its neck in an unconscious state. This is demonstrated separately by Eren, Ymir, and Annie when their Titan forms suffer defeat. But if a shifter's Titan form is not exhausted, then its human form can partially emerge from the Titan form in full consciousness. Annie, Ymir, and even Eren have shown this ability on three separate occasions.
The Titan Shifters also gain the Titan's ability to regenerate, capable of vastly improved healing abilities and even regenerating lost limbs even in their human forms. However, regeneration from severe injuries such as lost limbs can strain their powers and prevent them from transforming for a period of time. Both Eren and Ymir were unable to transform while recovering from their injuries, though Ymir is shown to have been able to transform within minutes of recovering.
It is also shown that they are not safe from regular Titans, and will be attacked even while transformed. Both Eren and Ymir were nearly devoured by hordes of Titans while transformed, and Reiner states that traveling while in Titan-occupied territory is dangerous to any of them. During the battle in Trost, it was shown that Titans seem to prefer to attack transformed Shifters. The human soldiers had great difficulty drawing away the Titans, as they were somehow drawn to Eren's Titan form.
A notable trait of the three major Antagonistic Shifters is their lack of skin, and special abilities unique only to their Titans. It is unknown how this relates to Eren and Ymir, who do not share their place of origin or purpose. In chapter 48, Ymir displays the ability to partially emerge from the nape of her Titan form, allowing her to interact with others while still transformed. It is unknown whether this is unique to her or a feat that any experienced Shifter can manage.
Revelations concerning Ymir's past in chapter 47 also suggest several important possibilities concerning the nature of Titans and Titan Shifters, as well as the existence of other Shifters. It is revealed that they do not age while in their Titan form, as Ymir notes she spent 60 years in her Titan form but has the appearance of a teenager. Although Ymir lacks complete and clear memory of this period, she recalls enough to describe it as an "endless nightmare." While trapped in her Titan form, she seems to have been a regular Titan that mindlessly devoured humans. Reiner and Bertolt do not treat this as an unusual case, and Bertolt notes that it was the same for them. Which leads to the conclusion that the first time of using their power they lack self decision and have only a decided goal, in Eren's case it was to kill Titans.
It also seems, from the experiments that Hanji conducted on Eren while in Titan form, that shifters are also vulnerable to absorbtion from their titan body, as prolonged usage of the form slowly decayed the mind and body of Eren up to the point where his human body lost its eyes and started to resemble his titan's. It may be possible that, since the titan brain is completely useless (as it can be blown off and the body will still operate), all the motor functions of the titan are completely carried by the human brain, greatly straining it, which in turn, may slowly oversaturate it leading to the loss of higher brain functions in favor of more mundane motor control, which also may lift any control the brain projected over the titan body to avoid absorbtion. Though Ymir is a notable exception, as even though she lost all cognitive functions, still avoided being absorbed, the case could also be for Reiner and Bertholdt and possibly even Annie. it may even be possible to reverse absorbtion.
Known Titan ShiftersEdit
Eren Yeager is the first Titan Shifter to be revealed in the series, his Titan being a 15m class. Its most prominent characteristics are its elongated ears, fleshless jaws and highly muscular build.
Unofficially named as the "Rogue Titan" due to its rampaging behavior, this form has so far been shown to have fairly substantial physical strength, knowledge of martial arts techniques, and incredible endurance. Prolonged and repeated use of this Titan form has allowed Eren to gradually increase control over its initially unstable mental state. Its eyes are a piercing grey in the manga, and teal-green in the anime; wherein they are often seen to be glowing bright green or blue. He also has a rage mode when he is seen fighting the Female Titan for the second time; this power grants him major strength, agility, and speed increase allowing him to do even more massive damage. In this rage mode there are distinctive characteristics, such as his eyes turning blue, his teeth becoming sharper and most notably being engulfed in fire.
Ymir's Titan is a small Titan of unknown height with long, black hair, very large irises and a chimpanzee-like body. This form grants Ymir rather long arms and sharp claws. It provides her with such a great agility that her form appears to be "dancing".
The smallest Titan Shifter yet known, this Titan form has a mouth full of pointed teeth, as well as sharp claws that can either be used to hang on walls or for combat. Its long arms and small muscular body enable it to maneuver itself around with great speed and agility in the same environments as those with 3D Maneuver Gear, making it a formidable force in battle.
The "Dancing Titan" is quite similar to the Ape titan and though Ymir spent 60 years as a titan, a soldier from Levi's squad is mistaken for Ymir and spends most of her time communicating with the titan until she is discovered to not be ymir.
Annie Leonhart can transform into a 14 m class Titan with a distinctively feminine build and short, blonde hair. Her transformation endows her with immense strength and speed.
A Titan Shifter of athletic appearance with lean muscle and no skin, the Female Titan is a Titan of unusual power and intellect. It has the stamina and focus to maintain a running pace capable of keeping up with horses over a long distance; as well as the intelligence to defend itself from multiple 3D Maneuver Gear attacks by prediction of the device's movements. This Titan form also has the unique ability to harden its skin by generating a crystalline substance across chosen areas of its body; allowing it to simultaneously protect its nape and fight. Combined with refined martial art techniques, it can perform incredibly deadly and destructive attacks. When cornered, the Female Titan's call has the ability to draw other Titans to it and drive them into a feeding frenzy.
Reiner Braun is capable of transforming himself into a 15-meter class Titan with a slight resemblance to his human form. Unlike the other Titan Shifters, his Titan form has very thick, hardened plates of skin all over his body which serves as his armor.
This type of Titan is well-built and has a hunched profile. Its only visible weaknesses are the small areas on the backs of its joints where there is no armor. Though not particularly fast, this form is strong and agile, capable of destroying a fortified wall after a sufficient running start. While he is able to communicate through roars, it is unknown whether he shares Annie's ability to summon other Titans.
The first Titan Shifter to appear chronologically within the series, Bertolt Hoover's Titan is of 60 m class. This grants him incredible strength like no other, capable of causing monumental destruction with little effort or damage sustained on his body. Due to this size its body temperature is extremely high, to the point that it is constantly emitting steam. However, because this Titan is so large, Bertolt can only move slowly while in its form.
It is the largest Titan seen so far in the series, four times the height of any other known Titan. This form has shown to be able to retain a degree of intelligence and tactical planning to go with its sheer size and strength, despite its slow movements. It is strong enough to break down the defensive walls surrounding humankind with a single and very hard-focused kick to allow other Titans to move inside the walls. It has the unique ability to superheat its body to produce incredibly hot steam as a defence. The heat of this steam is so intense that it is able to keep dozens of experienced soldiers at bay, lest they be cooked alive.
Little is known about the place where the majority of known Titan Shifters originated. It is said to be located somewhere outside Wall Maria, and is alternately referred to as the "village" or "homeland" of Reiner Braun, Bertolt Hoover, Annie Leonhart, and Berwick. It is one of the greatest mysteries of the series, with little revealed about it. Flashbacks to Annie's childhood show the clothing styles and housing are similar to that of the people living within Wall Maria. The only certainty is that there are in fact humans surviving outside of the walls, whether they are Titan Shifters or not.
The people from this land refer to themselves as being "warriors", a distinction also made when Ymir refers to them. While it is unknown whether all those living there are Titan Shifters, all three surviving characters from that location possess this ability. Ymir states that they possess the "Power of Titans", and she obtained her powers by stealing from them. As a result, she is a fugitive and greatly fears being killed by them should they catch her. She believes that Historia Reiss may be valuable enough to them to earn a pardon, and would not be harmed if surrendered to them.
In 845, they launched an attack against humanity and sent at least three agents into the Walls in search of the Beast Titan and something they refer to as the "Coordinate". However, Ymir believes that they possess influence even within humanity's lands, claiming that no one is safe from them regardless of where they might hide. Their agents are similarly desperate to complete their mission, going to suicidal extremes in their quest to obtain Eren Yeager even though they have expressed doubts that he is indeed the Coordinate.