|That did nothing! Eren's attack didn't... and my blades don't work either?! What's worse, unlike Annie, his whole body is hard!|
|— Mikasa struggles against the Armored Titan's power|
The defining feature of the Armored Titan is the all-encompassing layer of plated, armor-like segments of hardened skin protecting the Titan body. This armor is capable of protecting the Titan form from significant amounts of damage, even a direct hit from a cannon or the ultrahard steel blades of ODM gear.
One disadvantage of the Armored Titan's skin is the decreased speed of the Titan form. Whether due to increased weight or restrained movement, the Armored Titan is incapable of moving at high speeds when completely armored. This can be alleviated if the user chooses to shed segments of the armor to increase movement capability, such as the armor behind the knees.
The Armored Titan first appears in the year 845, shortly after the Colossal Titan first breaches Wall Maria, participating in the attack on Shiganshina district. During the chaos of the initial breach, it enters the city and makes its way across the streets to the interior gate. Once there, it charges towards the gate and smashes through it, allowing Titans to invade Wall Maria.
When Reiner, in a moment of exhaustion and desperation, reveals himself to be the Armored Titan and exposes Bertholdt as the Colossal Titan, the two transform into their Titan forms and battle against the Scout Regiment. Reiner's Armored Titan captures Eren Jaeger, descending from Wall Rose with the recruit in his grip until Eren transforms into his own Titan, ready to battle.
The Armored Titan initially overpowers Eren's Titan until it makes use of a throw that was taught to him by Annie Leonhart while they were cadets. This allows him close enough to grapple with the Armored Titan and break off his right arm. Eren retreats to the Wall to avoid capture, but the Armored Titan charges after it. Hange Zoë realizes that the Armored Titan cannot be completely armored if it is able to move that quickly and must have weak points like in the joints of a suit of armor. While the two Titans grapple, Mikasa Ackermann cuts through the back of the Armored Titan's knee, weakening its ability to fight. Eren's hold begins to break through the Armored Titan's plating, threatening to tear off its head. With defeat imminent, the Armored Titan roars, signalling Bertholdt's Colossal Titan, which falls on the two Titans. This allows Reiner the opportunity to bite Eren out of his Titan and escape while the Scout Regiment is unable to stop them.
Reiner and Bertholdt take a break in a Forest of Giant Trees, but when the Scouts pursue them sooner than expected they flee using their omni-directional mobility gear because Reiner says his Armored Titan is too slow. He refrains from using it until they get to the edge of the forest and then he transforms. Bertholdt, carrying a captured Eren, and Ymir in her Titan form, carrying Historia, ride on his shoulders.
The soldiers chase after them on horseback and Reiner is not fast enough to outrun them. When they begin attacking, Bertholdt calls for him to protect them and Reiner closes the Armored Titan's hands over Bertholdt and Eren so they cannot be taken away. However, he does not count on Commander Erwin Smith leading a horde of Titans into him.
Though he tries to charge through, the Armored Titan is overwhelmed and forced to a standstill due to the sheer numbers of Titans that grab on to him. Realizing that he will gradually be worn down, Reiner lifts his hands to bash away the Titans, though it exposes Bertholdt and Eren and ultimately allows Eren to be rescued.
Unable to immediately chase after the fleeing soldiers, Reiner begins throwing Titans at the Scouts in order to stop them, apparently not caring if Eren is eaten. Gradually, he removes enough that the Armored Titan can begin moving again. In the middle of the fighting, Eren strikes one of the Titans and activates the Coordinate that Reiner was searching for. Reiner charges at him, but Eren's outburst causes the Titans to focus their attacks on him and Bertholdt.
The Armored Titan survives the battle and Reiner retreats to Wall Maria along with Bertholdt and Ymir.