Attack Titan (Anime)

The Mysterious Titan (不思議の巨人) is the Titan form of Eren Jaeger. His Titan first appeared during the struggle for Trost and has become a symbol of humanity's newfound hope ever since.

Appearance
The mysterious Titan is a class with shaggy black hair, pointed ears, and an extremely muscular physique. The mouth of the Titan possesses no cheeks or lips, exposing a jagged row of many teeth.

The Struggle for Trost arc
After a Titan's arm bursts from the Bearded Titan's throat, out steps Eren from the Titan's back, transformed into a Titan himself. He then proceeded to wreak havoc on all the Titans he could get his hands on. In the process, he unknowingly saves the mourning Mikasa’s life and is baited by his classmates to help fend off a procession of Titans from a storage headquarters for the compressed gas used to power their ODM gear. As the Titans seem to overwhelm him and Mikasa’s group is about to intervene, the Titan that killed Thomas appears and Eren’s rage powers him to throw off the percussion and kill the Titan. As soon as the massacre is over, Eren falls to the ground and his human form emerges from the back of his Titan form’s neck (with both lost limbs back) to the shock of all the onlookers. He is retrieved by an overwhelmed Mikasa.

A plan is made for Eren to use his Titan form to move a huge boulder they had planned to use to reseal Trost's gate to prevent Titans from further entering, but were unable to move. Eren is assigned with a team including Mikasa to defend him while he carries the boulder. Upon his transformation to execute the plan, though, he attacks Mikasa, who tries to communicate with him to snap out of it, unsuccessfully. Eren ends up wounding himself and his body fails to regenerate, the mission is declared a failure. Despite this, the leader of the group, with some non-verbal convincing by Mikasa, decides they must stay and guard Eren.

Armin arrives on the scene and convinces Mikasa to go help fend off the Titans while he tries to get through to Eren. Eventually he is able to do so, by reminding Eren that they wanted to see the world together, causing Eren to remember how he wanted to join the Scout Regiment, and destroy all the Titans. Eren moves the stone and is able to plug the hole in the Wall at the sacrifice of the rest of the team members (with the exception of Rico, Armin, and Mikasa). They are saved from the desperate situation after Eren’s transformation back to human by Levi.

Assault on Stohess arc
After transforming into a Titan, the Mysterious Titan assists in capturing the Female Titan, as the two brawl out in Stohess, the Mysterious Titan nearly gets defeated until it grows into a state of fury. The Mysterious Titan then turns black and starts to burn as it goes to attack the Female Titan, it succeeds in capturing her by ripping her apart and biting the nape open.

Abilities
During the first Battle of Trost, Eren was swallowed whole by a Titan, and inside the stomach-like cavity saw other fellow recruits lying dead/dying, one wanting her mother before sinking in stomach acid. This sight combined with intense feelings of desperation and his drive to exterminate all Titans awoke his ability to transform into a Titan. In this form, he is a 15 meter tall Titan, with shoulder-length black hair, pointed ears, a long nose, and a gaping, skeleton like maw lacking lips. Unlike most other Titans, Eren's Titan form is considerably more muscular and defined; making him much stronger than even similar-sized Titans while his intelligence and military training, allow him to out-maneuver and dispatch entire groups of Titans with ease. A transformation takes a heavy toll on Eren’s body and requires large amounts of stamina. As a result, he has displayed several symptoms when he over-exerts himself such as a nosebleed, pale skin, and labored breathing. In some cases, Eren is rendered unconscious for a short period of time after a Titan transformation.

Initially, Eren has no control over his actions when he first transforms into a Titan and is unable to remember any actions that occurred during the first Battle of Trost. He is in a “dream-like state” and fails to remember how to transform in the first place. However, Eren recalls fragmented memories of his father by seeing the key to the basement of his old home and is able to successfully transform to protect Armin and Mikasa from certain death. It has been shown that with more transformations, Eren retains more of is intelligence being able to form rational thoughts. At the beginning, during the second Battle of Trost, Eren in his Titan form attacks Mikasa but ultimately plugs the hole in Trost's gate after Armin forces him to wake up. His Titan form, combined with his growing experience and his hand-to-hand combat skills, allowed him to kill over 20 Titans in his first transformation.

Eren, like all other Titan shifters, must physically harm himself in order to transform into his Titan form. However, lack of a determined goal and resolution for it inhibit his ability to transform as shown when he cannot transform at first to confront Annie Leonhart. Within Titan transformations, he has displayed the ability to partially transform, as shown when he protected Mikasa and Armin from a cannonball by forming the upper torso skeleton, complete with arms and a skull with some muscle tissue. From his suppressed memories, Eren believes that the full truth of his Titan powers, as well as a way to defeat the Titans once and for all, is located in the basement beneath the ruins of his family home.


 * Regeneration: Eren’s Titan form has demonstrated the ability to automatically heal any injury sustained in battle and also to regenerate entire limbs. Unlike Annie Leonhart, Eren has not shown the advanced ability to focus regeneration to one wounded area of his Titan form. His healing factor was fast enough to heal an entire lost hand in mere seconds to an entire arm in minutes. This ability is useful to Eren as, when he fights, he often loses entire limbs in his Titan form. While in his human state, Eren can also regenerate entire lost limbs, as seen after he lost his arm and leg to a Titan, he regrew them.


 * Enhanced Strength: As a result of Eren’s Titan form being much more muscular than other Titans, he is much stronger in terms of physical strength. During his first transformation, Eren was able to decapitate a 15m Titan with a single punch and kill a 7m Titan with little effort. With both arms lost, he was also strong enough to bite into the neck of a large, abnormal Titan that ate Thomas and lift it up above his head. With enough force, Eren was able to throw the abnormal into another Titan hard enough to knock them both into a building. Against the Female Titan in the Titan Forest, Eren’s Titan form had enough physical force to leave large craters in the ground, as well as lift the Female Titan into the air with a punch. Ultimately, Eren’s greatest display of strength was when he lifted a giant boulder, albeit with difficulty, carry it across a large distance, and slam it down to seal the hole in Trost's gate, producing a large shock wave.


 * Enhanced Endurance: Perhaps Eren's most notable trait of all is his ability to maintain levels of activity for an extended period of time. Eren’s first transformation carried on long enough to incapacitate 20 Titans in total. In battle, even after receiving massive amounts of damage from the Female Titan, Eren can carry on fighting, despite the handicaps that he suffers. He was also able to fight against the Armored Titan for a period of time and gain the upper hand. Eren’s endurance in his Titan form was enough to allow him to sustain the effort of hoisting a huge rock on his back, carry it over a large distance, and seal the hole in Trost's gate shortly before collapsing.