Fans who are up to date with Attack on Titan remember the shocking revelation that there are Colossal Titans within the walls. Following this discovery came one of the biggest mysteries in Attack on Titan, why put Titans in the walls? In hopes of uncovering answers, Eren and the others continue their pursuit to Grisha Jeager's basement. It wasn't until episode 19, season three, "The Basement," that the answers were revealed.
From the books found in Grisha's basement, the Scouts discovered that the Colossal Titans were put within the walls of Maria, Rose, and Sina by King Karl Fritz. One hundred years ago, Karl Fritz was the 145th King of the Eldian Empire. During this time, the eight families who held the power of the titans fought in an endless war. It was the job of the Fritz family, who possessed the power of the Founding Titan, to keep the empire in check. The never-ending fighting and bloodshed caused Karl Fritz to have a mountain of grief, leading to the creation of the Wall Titans.
Millions Trapped Within The Walls
Karl Fritz believed that the Eldian Empire had done more harm than good. Memories from the Founding Titan showed him what his predecessors had done, riddling him with guilt. No longer wanting to partake in the conflict, Karl Fritz took the royal family and many Eldian's to Paradis Island. Here they would be safe from war, and eventually, the Eldian Empire would be destroyed with no king to rule. According to Willy Tybur, the walls were created by King Fritz as a threat to the outside world. Using millions of his people, King Fritz created Titans similar to the Colossal Titan to create the wall.
When the wall was complete, King Fritz sent a message out to the world, if any were to attack the inhabitants on Paradis Island, then the Wall Titans would be released to flatten the world. The fear of Millons of Titans being released from the wall kept Paradis Island safe for a time, but no one would remember any of this because Karl Fritz erased the memories of all the Eldians within the walls as one final act. Those behind the walls forgot the threat of the Wall Titans, but for those in Marley, the danger was considered too significant for a time.
Why, then, would the new holder of the Founding Titan not release the Wall Titans when Marley began dumping Pure Titans onto the island? The reason is that King Fritz never intended to release the Wall Titans, according to Willy Tybur. The threat was a bluff intended to keep the people on Paradis safe for as long as possible, but if they were to be attacked, King Fritze never intended to stop them. Along with memories, possessors of Titan powers are also persuaded by their predecessors' beliefs, meaning all the Founding Titan holders after Fritz would be compelled to not release the Wall Titans. The only question then is, why create the Wall Titans at all if King Fritz never intended to use them?
What Could Be The Real Purpose of the Wall Titans?
During season one, fans learned that some Titans could have special abilities, like the hardening of the skin. Having the Founding Titan ability, King Fritz had the power to create the Wall Titans with the capability of hardening their skin. Millions of Eldians joined together and hardened their skin to create the three walls, all under the order of King Fritz. Why would Karl Fritz do this to millions of his own subjects, knowing no one in the Fritz line would ever release these Titans? Perhaps King Fritz knew none of his descendants would release the wall titans, but instead someone not of his bloodline would fulfill his warning. What if those who possess a Titan ability can see the memories of the future holders as well as those of the previous holders?
At the end of episode 21, season three "Attack Titan," Eren Kruger is preparing to give Grisha Jaeger the Titan serum so that Grisha can devour Kruger and inherit the Attack Titan. During this time, Kruger implores Grisha to fall in love and have a family in the wall to stop the cycle of hate. Grisha isn't interested, having just watched his wife Dina transform into a Pure Titan. Kruger implores Grisha to fight on and save Mikasa and Armin with some unknown determination. How would Eren Kruger know anything about Mikasa and Armin (they hadn't even been born yet) unless he wasn't remembering his own memories? Kruger comments on this after realizing that they weren't his memories.
Could all of this mean that the possessors had known the events of Attack on Titan of the Titan abilities? Did Karl Fritz see the future from the new holder's memories, and know that the Wall Titans would be needed for the future. What does this mean for the final season of Attack on Titan? Readers of the manga will know, but until then anime viewers will have to wait and see what happens to the Wall Titans.