Power of the Titans (Anime)

"What are you? A man? Or a Titan?"

- Kitz Woerman to Eren Jaeger

Titan shifters are humans in possession of the Titan ability (巨人の力), which allows them to transform into Titans. Unlike regular mindless Titans, they are able to control their form and retain their human intelligence. It is often noted that these Titans are far more powerful than regular Titans and oftentimes display abilities unique to only them.

Transformation
In order to transform, a human with the Titan ability must suffer an injury that draws blood (often self-harm) while having a solid goal or belief in mind at the moment of injury. However, being injured by another person is also sufficient. Once the transformation is initiated, a burst of energy is released (in some cases as a bolt of lightning or an explosion), followed by the generation of the Titan body and a release of hot steam. After transformation, the human body rests within the nape of the Titan's neck, the center of control. The human body is also merged with the Titan's flesh inside to varying extents, most frequently on the area of the cheeks below the eyes, rendering them immobile. If a Titan form is pushed to its limit, the human will emerge from the nape of its neck, sometimes in a semi-conscious or entirely unconscious state. But if a Titan form is not exhausted, then its human form can emerge from the Titan form in full consciousness. In some cases, a human is able to partially emerge from their Titan body without fully leaving the nape.

When the power of the Titans is used, oftentimes the area around the emerging human's eyes is marked by dark lines for a short time after. The amount of time the human possesses these marks appears to depend on how long, skilled, or overworked they used their Titan forms, ranging from several minutes to several hours.

In some cases, the ability to transform into a Titan is hindered by injuries inflicted on the human body. A human can transform into a Titan with injuries as severe as a missing limb, but only if a previous transformation has not occurred recently. If a human emerges from their Titan form and receives severe injury, this person cannot transform into a Titan again until said injuries have fully healed.

Physiology and abilities
The average height among the transforming Titans is 15 meters, but this can vary greatly, ranging from the 4 meters of Annie's Titan form to the 60 meters of the Colossal Titan.

Humans with the power of the Titans also gain the Titan ability to regenerate and are capable of vastly improved healing abilities, even to the point of regaining lost limbs. However, regeneration from severe injuries such as lost limbs can strain their powers and prevent them from transforming for a period of time. It is evident that healing for a Titan's human form takes much longer than their Titan form. The time it takes to regenerate appears to depend on the extent of the injury and how focused the individual is on healing that area.

It is also shown that these Titans are not safe from regular Titans, and will be attacked even while transformed.

While not all Titan abilities have been identified, each inheritable Titan possesses a unique power. The Colossal Titan has been shown to possess significant control over his body, able to release devastating gusts of steam to ward off enemies or even completely evaporate his Titan form in seconds. The Armored Titan possesses hardened armor-like skin covering all but the key areas of movement. The Female Titan is able to call upon mindless Titans with a scream, luring dozens towards her position with little time. The Beast Titan is able to control Titans to a small extent.

Annie's Female Titan has been shown to possess the ability to harden her skin to the point of near indestructibility. She is able to selectively harden regions of her Titan body and even create a hard crystal around her human body, putting her in an apparently unconscious state with no need for nutrient intake. In addition to the armored plates covering the Armored Titan, it too is able to control some hardening aspects of his Titan such as creating claws on his fingertips. It seems, however, that not all transformed Titans possess this hardening ability.

Trivia

 * Many transformed Titan forms are modeled after mixed martial artists. For instance, the Armored Titan is modeled after and Eren's Titan is modeled after.