|What are you? A man? Or a Titan?|
|— Kitz Woermann to Eren Jaeger|
The power of the Titans (巨人の力 Kyojin no Chikara?) is the ability which allows for humans to transform into intelligent Titans. Unlike regular mindless Titans, those with the power of the Titans 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.
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 (usually a bolt of yellow 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.
After the power of the Titans is used, 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 a 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 5 meters of Ymir'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 that of 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 its body, able to release devastating bursts of steam to ward off enemies or even completely evaporate 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.
Annie's Female Titan has also 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. It seems, however, that not all transformed Titans possess this hardening ability.