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|Karl Fritz used the power of the Founding Titan...to give birth to massive Titans. These were to act as both his shields and his spears.|
|— Willy Tybur recounting the past|
The Wall Titans (壁の巨人 Kabe no Kyojin?) are Abnormal Titans similar in appearance to the Colossus Titan, one of the Nine Titans. They possess the ability of crystallization and exist in vast numbers composing the three Walls, before Eren Yeager freed them in the year 854.
In the year 743, King Karl Fritz used the power of the Founding Titan to create and command "tens of millions" of these Titans to create the three Walls and protect the last Eldian territory on Paradis Island. The lack of sunlight inside the Walls has supposedly rendered them immobile ever since, although King Fritz "threatened" to release them and use them to flatten the Earth should Paradis Island come under attack.
These Titans are similar in appearance to the Colossus Titan in that both their surfaces are covered primarily in muscle tissue and lack skin (although the Colossus Titan typically has more bony tissue exposed around its face). Like the Colossus Titan, they all share the long arms and elephantine feet necessary to support their structures. Each Titan varies slightly, most noticeably around the face; some possess very defleshed faces, while others exhibit complete musculature. Their exact heights are unknown- and likely vary somewhat- but they are about the height of the Walls, which were 50 meters tall.
Like other Titans, Wall Titans generate great amounts of heat, enough to emit large plumes of steam not unlike the Colossus Titan. They can use this ability both offensively and defensively, creating smokescreens and flash-boiling seawater to incinerate entire battleships. All Wall Titans possess the ability to harden, although it is probable that they only did so because they were commanded to by the Founding Titan. This hardening was used to mold the surface of the Walls, with the Wall Titans acting as their central pillars.
Their speed on land is estimated to surpass that of a galloping horse. They are also capable of maintaining this speed in water, as the entire horde crossed the ocean between Paradis Island and the mainland within a few days. The Titans are extremely tough, with very large naval cannons being the only weapons capable of injuring them.
Like the Colossus Titan, their sheer size and mass enables them the capacity for great destruction; with a single step, a Wall Titan is capable of collapsing buildings and pulverizing humans underfoot. This physical ability, coupled with the sheer number of Wall Titans, is the basis for Paradis' main deterrence, the Rumbling.
In the year 743, after King Karl Fritz abandoned the conflicts of Eldia causing the Great Titan War, he fled overseas with the main branch of the Fritz royal family and remnants of the Eldian populace to Paradis Island, Eldia's last remaining undisputed territory. He used the power of the Founding Titan to create and order tens of millions of Wall Titans to form the three concentric Walls to protect the Eldians. The King sent a message to the people of Marley, demanding that the Eldians on Paradis Island must be left alone or else the Wall Titans would "flatten the entire Earth."
During the battle betweenEren Yeager and Annie Leonhart in the Stohess District, Annie attempts to escape by climbing the Wall but is stopped by Mikasa Ackerman. However, she damages part of the Wall, and a huge chunk is torn off, revealing the face of a mysterious Titan.
The missing chunk of the Wall is immediately noticed by Mikasa. The Titan within the Wall follows Mikasa's gaze, and Minister Nick calls for the immediate covering up of the Titan, as the sunlight eventually might eventually awaken it. After Nick ignores Hange Zoë's questions about it, he is nearly thrown off the Wall by Hange, but still refuses to reveal any details he might know because of the Church of the Walls' secrecy.
In the Reiss Chapel, Rod Reiss explains how the First King used the power of the Founding Titan to form the three Walls which surround humanity's territory, though the Wall Titans are not mentioned.
After the surviving Survey Corps reach Grisha Yeager's basement, they learn from his books about the story of the formation of the Walls as it was told to the Eldian Restorationists by Dina Fritz.
During the festival hosted by the Tybur family, Willy Tybur tells the world of the truth about the Walls, the Great Titan War, and King Karl Fritz. He reveals that due to the King's vow of pacifism which prevents the Founding Titan from being used for war, the Wall Titans were never a true threat. However, due to a coup d'état in recent years, the military of Paradis Island have overthrown the previous royal government and rendered the King's ideology of peace ineffective. Now that the Founding Titan belongs to Eren Yeager, who is seemingly capable of using its powers despite not having royal blood, and without interference from King Fritz's will, the world is truly in danger of the Wall Titans for the first time. Eren himself admits this to be true.
As the Royal Government discusses Zeke Yeager's requests which were brought to them by the Anti-Marleyan Volunteers, Eren Yeager reveals he is able to activate the powers of the Founding Titan by coming into contact with a royal-blooded Titan. He also states that this method can be used to awaken the Titans within the Walls without invoking the vow of renouncing war.
After Kiyomi Azumabito arrives on Paradis Island, she divulges the rest of Zeke's strategy to save Eldia which involves unleashing some of the Titans inside the Walls to demonstrate its destructive power. The island would then need to keep that power in reserve for the next 50 years as Eldia advances technologically.
Following Zeke's encounter with Eren, Eren successfully frees Ymir from her enslavement and invokes the Founder to begin the Rumbling. The Walls crumble, and the Wall Titans begin to march under Eren's command to eradicate all life outside the island.  As they make their way towards the outside world, they inflict collateral damage in the areas formerly within the Walls, mindlessly demolishing buildings and killing civilians. Within a few days, the last of these Titans have left the cities of Paradis.
By the time the combined force of the remaining Survey Corps and Warriors reach the harbor, the Titans are long gone from Paradis, their plumes of steam having receded over the horizon. Hange Zoë predicts that the Titans would be able to reach the coast of Marley and annihilate the cities closest to Paradis in the span of a few days. As half a day is required to service the flying boat, they decide to replot their course towards Odiha to buy some time.
The Titans nearing the Marleyan coast eventually encounter a naval blockade: The Global Alliance Fleet. The battleships begin bombarding the horde, who are swimming just below the surface. Few shots land, and fewer still do lasting damage. The Titans easily bypass the blockade, and as they pass under the warships, they unleash bursts of heat, instantly boiling the seawater around them and scorching the ships' crew to death. A thick haze obscures the harbor, hiding the coast from the view of the artillerymen defending the land. As the smoke clears, the Wall Titans rise out from the water and the remains of the naval fleet. The land artillery begin their barrage, but to the soldiers' shock, it is ineffective as well. As the artillerymen desert their posts and retreat towards higher ground, they spot Eren's Founding Titan following the phalanx of Wall Titans.
As the Titans march, Eren recalls his mother's death, and the vow he made that day to keep pushing forward until he destroys every last one of his enemies. As he does so, the Wall Titans take their first steps on Marleyan soil, marking the beginning of the prophesied Rumbling.
The Wall Titans make their way further inland, eventually reaching the seaside town infiltrated by the Survey Corps some months before. Encircling the town via the mountains surrounding it, the Titans annihilate the settlement with the civilians who were unable to escape. As they leave the cratered remnants of the town, a youthful incarnation of Eren reminisces on his childhood: confined by the Walls and inspired by the descriptions of the outside world from Armin Arlert's book; his thoughts compounded with the spectacle of the Titans' carnage. He then states he has reached freedom, and, turning around, asks Armin's opinion of it through the Paths.
The Wall Titans continue their long march through the continent's interior, eventually nearing the port city of Odiha. As they lumber towards it, a lone soldier rises up to face them. A few Titans are felled, but the soldier quickly succumbs to the intense heat of the Titans' bodies. The Titans proceed to crush Odiha underfoot.
In Rikao Yanagita's analysis of the Attack on Titan manga, an estimation of the amount of Wall Titans residing within the Walls is given. Using the dimensions given in Attack on Titan: Before the Fall, Rikao estimates that, if the Wall Titans are all approximately 45 meters in height with a proportional 13-meter shoulder width with all Titans lined up shoulder to shoulder, there are approximately 246,000 Wall Titans within Wall Maria and a total of 585,000 Titans within all three Walls combined. This conflicts with information given much later in the manga in Chapter 86, in which King Fritz's ultimatum given to Marley states that he would unleash the "tens of millions of Titans that sleep inside the Walls" if war was declared against Eldia. Furthermore, Paradis Island's evident correlation with the real world island of Madagascar leaves no room for Walls of the sizes given in Before the Fall, meaning there may be even fewer Titans within the Walls than Rikao's estimate and Karl Fritz's claim.
- Taking Hange's estimate of the Wall Titans traversing 600 km of land in half a day, we can deduce that they are capable of sustaining 50 kph, indeed slightly faster than a horse's gallop.