Power of the Titans

Titan Shifters are specific humans in possession of the "Titan's power" (巨人の力), which allows them to transform into Titans. Unlike regular Titans, they are able to control their regular form and retain their human intelligence. It is often noted that Shifters are far more powerful than regular Titans.

Description
To transform, they must suffer an injury that draws blood (often self-harm, 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 the inside of 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. Once the transformation is initiated, a yellow bolt of lightning appears to strike down the Shifter from the sky, followed by the generation of the Titan body and a release of steam. After 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, rendering them immobile. It is also visible that their eyes are connected within the body of the Titan, presumably for optic vision outside the body.

If a Shifter's Titan form is pushed to its limit, its human form will emerge from the nape of its neck in a semi-conscious 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. When a Shifter emerges from their Titan body, the area around their eyes is burned from the hot muscle of their Titan forms for a short time after. Every Shifter with a known Titan form has exhibited this at least once, with the exception of Grisha Yeager.

The Titan Shifters also gain the Titan's ability to regenerate, capable of vastly improved healing abilities and 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. Healing for a Titan Shifter's human form takes much longer than a Titan, as it took Ymir several hours to regenerate her limbs and it took Reiner a night to regenerate his broken arm.

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 of Trost, it was shown that Titans seem to prefer attacking 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. 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 over time.

Revelations concerning Ymir's past 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-determination and have only a decided goal, devour humans. In the case of all the currently known Titan Shifters, excluding Ymir, it appears that there was a Shifter present for them to devour. With only Eren, Frieda, and Uri having the Shifter they ate being shown or mentioned.

Experiments performed on Eren suggest that Shifters are resistant, but not immune to the normal absorption that creates mindless Titans if they stay transformed for a long time. After one hour to be transformed, Eren entered in a state of pain and eventually left his Titan body. With the the two subsequent transformations after short rests, the strength and quality of his Titan form degraded more and more, becoming smaller and less controlled each time. On the third transformation, his lower body remained free while his upper body began to merge with his Titan form. It became necessary to cut him loose, removing most of the tissue from the front of his skull in the process. As such, it seems that there is a limitation on how long a Shifter can remain in a transformed state before risking absorption.Similarly, it seems the longer or more often a Titan form is used and how exhausted the human within is, the more difficult the form can be to consciously control. This may cause the Shifter's form to regress to typical Titan behavior and can make them unpredictable if weaponized.

Their powers can be transferred to a new host, should they be devoured. This allows an ordinary Titan to become a new Titan Shifter, should they succeed in devouring one—as was the case when Ymir devoured Marcel and regained human form. Hange Zoë theorizes other abilities, such as the Coordinate possessed by Eren, could be transferred to a new host in the same fashion.

Grisha Yeager, a Shifter himself, was capable of using a syringe to turn a young Eren into a Titan which in turn devoured most of his body. Similarly, Frieda Reiss became a Titan via syringe in order to consume her uncle to become a Shifter and to obtain the Coordinate ability. The serum induced Titans resemble regular Titans but with a slight resemblance to the human host. Rod Reiss revealed that Titan Shifters, who have been given their abilities by having to devour someone, have a chosen Titan Shifter form for them to take. Rod Reiss also reveals that certain serums can create a different type of Titan with different abilities. For instance, Eren consumed a bottle from Rod's bag labeled "Braun" which gave his Titan the power of skin hardening at will.

Notable Titan Shifters
This is a list of known Titan Shifters who's Titan form has yet to be shown in detail:


 * Marcel
 * Uri Reiss
 * Mr. Reiss
 * The First King