Colossus Titan

"You're facing humanity's greatest enemy! All troops, attack!"

- Hange Zoë leads an attack on the Colossus

The Chō ōgata Kyojin (超大型巨人) is one of the Nine Titans noted for its incredible size and significant control over the steam emitted by the Titan form. It is currently in the possession of Armin Arlert.

Steam emission
The unique ability possessed by the Colossus Titan appears to be significant control over the amounts of steam emitted by the Titan form. In normal circumstances, Titans emit steam from wounds, and their bodies evaporate completely into steam after receiving a killing blow. The Colossus Titan is capable of emitting great amounts of steam at will. This power can be used for a variety of purposes. By emitting great amounts of steam at once, the pressure and force of the steam will burn and repel any individuals in close proximity to the Colossus Titan that are not fixed in place.

However, prolonged use of this ability takes a toll on the Titan, decreasing muscle mass gradually until only the skeletal structure remains. In some cases when it is necessary, the Colossus Titan is capable of evaporating its entire body at once, disappearing instantly. This puts the user in a position of great vulnerability, with no way of preventing a fall from a great height where the Titan form once was. However, this disadvantage can be alleviated if the user is wearing vertical maneuvering equipment.

Size
Bertolt Hoover's Colossus Titan was infamous for its incredible size, standing at a previously unseen, high enough to peer over the top of the Walls. While the mindless Titans which form the foundations of the Walls also possess incredible height and a lack of skin similar to Bertolt's Titan, despite the former not possessing the power of the Titans, it appears that the size of the Colossus Titan is also a trait which is inherited in each successor, as evidenced by Zeke Yeager's opinion that an individual with the power of the Titans inherited from Bertolt provided assistence to Eren Yeager in destroying the 32 Marleyan scouting ships sent to the island of Paradis.

History
The Colossus Titan, like all the Nine Titans, was brought into the world after the death of Ymir Fritz. In the 1,700 years following her death, the Colossus Titan was held in the possession of one or several of the warring Eldian houses subservient to the Founding Titan. After these seventeen centuries when the 145th King of the Fritz family abandoned the conflicts of Eldia and relocated to Paradis, the Colossus Titan was taken by the nation of Marley during the Great Titan War.

At some point before the year 845, Bertolt Hoover was chosen to inherit the power of the Colossus Titan. Some time later, the nation of Marley sent out Bertolt, Reiner Braun, Annie Leonhart, and Marcel Galliard across the ocean to the island of Paradis as the start of the Paradis Island Operation.

The Fall of Shiganshina arc
Bertolt transformed into the Colossus Titan outside the southern gate of Shiganshina District, the southernmost territory of Eldia. Using his immense size, Bertolt's Colossus Titan breached Wall Maria in one kick, allowing for the many Titans awaiting outside to enter into Eldia's territory. Bertolt joined his fellow surviving warriors in entering the walled territory during the chaos.

Battle of Trost District arc
Five years after the fall of Wall Maria, Bertolt and his allies graduate from the 104th Training Corps. The next day, Bertolt transforms into the Colossus Titan outside the south gate of Trost District, breaching the Wall as he did five years before. Before he can escape, his Colossus Titan is confronted by Eren Yeager seeking vengeance. Eren attempts to strike at the Colossus, but Bertolt makes use of his steam emission control and prevents Eren from getting close. As Eren fights against Bertolt's steam and comes in for the killing blow, the Colossus Titan evaporates instantaneously. As Eren attempts to comprehend the situation, Bertolt escapes under the cover of his Titan's steam using his vertical maneuvering equipment.

Clash of the Titans arc
Due to the discovery of Eren's possession of the Attack Titan, the warriors postpone their plan to destroy the Walls and instead focus on capturing Eren, whom they believe possesses the Founding Titan as well. Bertolt does not make use of the Colossus Titan until a month after the battle of Trost District, when Reiner in a moment of exhaustion and desperation reveals himself to be the Armored Titan and exposes Bertolt as the Colossus Titan. With nowhere to run, the two transform into their Titan forms and battle against the Survey Corps. As Reiner's Armored Titan battles Eren's Attack Titan, Bertolt fights against the soldiers of the Survey Corps with a partially transformed Colossus Titan. When the soldiers are ready to land a killing blow, Bertolt once more uses his steam emission control to keep them all at a distance, and their vertical maneuvering equipment is unable to reach him in the continuous gusts of wind. Bertolt's Colossus remains in this state of emission for a short time until Reiner faces imminent defeat in his struggle against Eren and calls for help. Hearing Reiner's signal, Bertolt falls to the ground below and evaporates his Titan in an explosive gust of steam. In the chaos, Reiner steals Eren from his Titan, and Bertolt joins him after leaving his Colossus.

Return to Shiganshina arc
The warriors fail in capturing Eren and later flee to the ruins of Shiganshina District. For two months, Bertolt presumably does not use his Colossus Titan until the battle of Shiganshina District, where he prepares to transform into his Titan above the district in order to destroy the city. However, his plan is stopped short after seeing Reiner alive and in peril, and he transforms at a later time after speaking with his former fellow recruits. As the Colossus Titan, Bertolt begins setting fire to the houses of Shiganshina with his Titan's heat and sends the structures soaring through the air, bringing great devastation to the town. Eren attempts to attack the Colossus, but his attempt is short-lived when he is kicked to the top of Wall Maria. The recruits of the Survey Corps attempt to attack Bertolt with their Thunder Spears, but the Colossus' steam emission keeps them away. However, at this time Armin Arlert notices the loss of muscle mass brought on by each steam blast and formulates a plan to defeat Bertolt. Armin brings Eren back into consciousness and informs him of his plan to defeat Bertolt. Knowing his maneuvering equipment will not stay attached to the Colossus' evaporating flesh, Armin grapples to the teeth of the Titan as Eren collapses to the ground below. Wanting to kill Armin quickly, Bertolt emits a huge amount of burning steam at Armin, roasting him alive until he can no longer remain grappled to his Titan. Armin collapses to the ground below, and Bertolt turns his attention to Eren. He notices too late that Eren's Attack Titan on the ground below is in fact merely its hardened shell, and in the moment of vulnerability Eren strikes at the Colossus Titan from his human form, pulling Bertolt from the nape as the Colossus Titan collapses in defeat. On the rooftops of Shiganshina, the surviving members of the Survey Corps are left with the choice of using a Titan serum in their possession to save either Armin or Commander Erwin Smith from the brink of death. The choice is left to Captain Levi, and after some hesitation he chooses to save Armin's life. As a mindless Titan, Armin grabs Bertolt as he comes back into consciousness and begs for his life. His cries go unheard, and Bertolt is eaten alive by Armin's Titan.

Through the years 851 to 854, the nation of Marley sent a total of 32 scouting ships to the island of Paradis, all of which ended up missing. While the details concerning their disappearances are currently unknown, Zeke Yeager theorizes that the Attack Titan as well as another Titan under Paradis' control, likely Armin Arlert's Colossus Titan, are responsible for the ships' disappearances.