For long periods of time, Paradis was a protected island. Paradis was secured by walls of toughened Colossal Titans. In a time of always advancing in technology, the Colossal Titans provided Eldia’s only hope against those who would like to destroy it.

In the event that it was announced that the Eldian people were relocated to Paradis the Karl Fritz, the King of Paradis Karl Fritz declared that if Paradis was ever to be attacked and the Titan who was the Founding Titan will unleash the Wall Titans into the world and wipe out the entire planet.

This event would later be called The Rumbling.

The threat was effective because the idea of millions of Colossal Titans marching on humanity was frightening. 

Yet, to the majority of people, Karl Fritz had no intentions of creating such a devastating incident. In a pledge to the Founding Titan, the King had given up war, assuring the future heirs of his would not be free from damage to anyone in the universe.

In the final chapter the Attack On Titan Manga, Eren Yaeger was able to bring the doomsday scenario to life. It killed over 80 percent of the world’s people.

What are The Three Walls?

The wall that is the outermost one is known as Maria. It’s the initial barrier between Paradis and the world at large. 

The second wall inside Maria is known as Rose and is a barrier that divides families of the upper class from the lower-class families. A third wall called Sina is what separates royalty from the wealthy.

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The name is derived from the origin of the wall.

The three walls of circular form which are a part of Paradis Island were named after the daughters of Ymir who was the very first Titan.

They are 50 meters high and, for the most part, unbreakable. Thus, they serve as a defense against Paradis and Pure Titans trying to cause trouble.

The walls also had their own churches and were worshipped religiously by the “Wallists”, who believed they were the protectors of humanity.

At the time of the beginning in the AoT sequence, human beings in the walls did not know of the existence of Titans in this. 

At the will of the Founding Titan, hundreds of Colossal Titans had hardened themselves to create a barrier to the world outside. 

Only under the guidance of the Founding Titan could it be possible to liberate the Colossal Titans and then use them to trigger The Rumbling.

What is the Purpose of Rumbling?

The Rumbling was a blatant bluff from King Karl Fritz to protect Paradis for as long as he could.

Although he stated that the Eldians had the power to use their Wall Titans to flatten the planet and make it a slum, King Fritz had taken an oath that prevented the successors of his from using the Titans.

Karl admitted the possibility that an oath such as that could leave Paradis vulnerable in the future. He believed, however, that due to the Monarchy’s previous crimes the possible future is inevitable and well-deserved. 

Thus, his primary aim was to defend his people as long as was possible, and, after that, they would have to pay for the sins of their forefathers.

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What were the Conditions to Activate the Rumbling?

Eren and Zeke

There were two requirements to meet in order to start The Rumbling.

First, it was that it was only one person, the Founding Titan could command the Wall Titans and unleash them on the world.

The second reason is that to allow to have the presence of Ymir to fulfill the wishes that were enacted by the founding Titan the person who carried the Titan must be blood royal.

The second requirement was directly in contradiction to Karl’s oath, however.

Since Karl Fritz renounced violence, no descendant of his could command the Wall Titans to commit destruction. This is why The Rumbling was considered an “empty threat.”

However, things took a drastic change when Eren came into possession of the Founding Titan.

This is the reason Eren-Zeke’s on-the-run partnership was so crucial to the story.

Because Eren was not a royal He wasn’t legally bound by Karl Fritz’s vow of non-violence. He was, however, not able to utilize his full powers as the Founding Titan to command the Wall Titans.

On the contrary, Zeke’s royal heritage could allow him to lead Ymir to unleash the Titans. However, the oath he took prevented Zeke from doing this.

Together, they could both bypass these limitations and start Rumbling. Rumbling.

Eren discovered later that the real goal of Zeke is to eliminate those who were Subjects to Ymir and that, in spite of the royal’s orders his own was not sufficient. Without a choice, Eren then convinced the spirit of Ymir to let her go of her vow to serve the royals. This in turn triggered the Rumbling.

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What Happened After The Rumbling?

After seeing Mikasa cut off Eren’s head, Ymir decided to let her hold on the founding Titan and put her place in Rumbling and the power of all Titans. 

Ymir noticed herself in Mikasa’s affection for Eren and was relied on Mikasa’s choices to make a decision she would never be able to make.

A few years later, after the Rumbling the world was at peace. It was the time when the Marleyen administration sent its ambassadors over to Paradis to begin peace talks. 

When they arrived they were informed that the Yaegerists who remained had put together an army to defend Paradis from outsiders.