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Bertolt Hoover also known as The Colossal Titan is one of the main antagonists in Attack on Titan.
The Colossal TitanThe largest Titan ever encountered, having first appeared in the Year 845 outside the District of Shiganshina. It is approximately 60 meters tall with a physical appearance resembling a humanoid being without any skin, exposing muscles and connective tissue. In addition, it has not shown any interest in consuming humans. It appears suddenly and without warning in a flash of lightning, and disappears in a similar manner in large clouds of steam, which
constantly pours from most parts of its body. It possesses the ability to release this steam at high pressure to defend the weak point at the base of its neck. Possessing a physical mass far larger than any other known Titan, it was easily able to kick down the Gate into the District of Shiganshina and thus is partially responsible for the fall of the Wall Maria. It displays cognitive recognition when it appears before the District of Trost in the year 850, as after kicking down the gate into the district, it destroys the cannon artillery atop the wall so that the invading Titans would meet less resistance.
Bertolt comes from a mysterious location simply referred to as his hometown (or homeland), and began a mission to attack humanity in the year 845. Little is known about his life prior to undertaking his mission, other than the fact that Reiner and Marcel were his childhood friends. The exact nature of their group, and their mission is yet unknown. It is mentioned that their goal was to exterminate humanity, and that they are searching for both the Ape Titan and a "coordinate" which they believe may be Eren Yeager or possible to locate with the assistance of Historia Reiss.
At some point prior to attacking Wall Maria, he encountered Ymir's Titan form while traveling with Reiner and Marcel. Still in a mindless state, she attacked the three boys and nearly killed Reiner. Marcel ended up sacrificing his life to protect his friends, while Bertolt appears to have fled in terror and possibly abandoned the other two in the process.
Fall of Shiganshina
Bertolt first appeared as the Colossal Titan in the year 845, shortly after the history of the world and humanity's situation have been introduced, along with Mikasa, Eren and Armin. Its mere presence is enough to cause considerable panic amongst the population, as it is tall enough to see completely over the wall that is supposed to keep all Titans out. Within moments of its appearance, it attacks, repeatedly kicking the wall gates to the point that they rupture and open a hole large enough for other Titans to pass through. It then disappears after causing considerable structural damage to the wall, but does not attempt to participate in any meaningful way in the ensuing massacre itself.
Joining The Military
Eventually, Bertolt joined the military, with aspirations of joining the Military Police and living in the safety of the inner wall. As part of the 104th, he was considered to be one of the best in regards to 3D Maneuver Gear, enough so that Eren Yeager came to him for advice when he was dealing with faulty equipment. After seeing Eren's determination and desire to join the Survey Corps, he considered himself a coward for wanting to get far away from them. However, Eren encouraged him, saying that after witnessing the attack on his village, no one would blame him for his decision. Eventually, he graduated in the top ten of his class coming in at third place, just under his friend Reiner.
Battle of Trost District
Bertolt reappears as a Titan five years later in 850, again breaking through the walls so that its brethren can once again devour the humans inside. It is immediately attacked by Eren Yeager, however, it first repels and blinds him with vapor from its high temperature body before vanishing completely from view.
When Armin, Mikasa and Connie made it to the headquarters, with the help of the Rogue Titan, Armin devised a plan to get rid of the Titans in the supply room. Bertolt, part of the second group, came in from the ceiling and killed his target in one blow. The mission a success and everyone resupplied, he and the rest of the group leave the head quarters. On the way out, he joins Mikasa and others on the rooftop as they watch the rogue Titan being attacked and eaten by other Titans. Reiner suggests helping it out, but ultimately it ends up not being necessary as the Titan fights his way out and kills the Titan that ate Thomas. After the Titan collapses, he is among the first people to know about Eren's ability. Bertolt joins the Survey Corps with Mikasa, Reiner, Eren, Connie, Sasha, Krista, Armin, Ymir, Jean and a few others.