Later in the episode, we see that Eren also takes the Armor Serum by breaking the vial by his teeth and taking the serum via his mouth - which is again the wrong way.
In desperation, Rod licks the exposed serum, becoming a monstrous Pure Titan. In order to save his comrades from the collapse of the Chapel's caverns, Eren bites into an injection vial labeled "Armor," granting him the ability to harden his Titan.
Unbeknownst to anyone, including Eren himself, the contact with Dina Fritz - a Titan with royal blood - causes Eren to briefly activate the power of the Coordinate in the Founding Titan.
After hearing this, Grisha takes Eren into a nearby forest and instructs him to go to the basement; before Eren can react, Grisha injects him with a Titan serum, turning Eren into a mindless Titan. Eren instinctively eats his father, receiving his Titan powers, including the dormant Founding Titan.
Attack on Titan: Five times Eren went wild
However, his best friend, Armin, is about to be eaten by a Titan, a painful death for anyone. So, with will and pure determination, Eren reaches into the Titan's mouth and pulls Armin out. Eren then gets eaten about a second later, but hey, he gets out.
If that were indeed the case, Sasha's death would have confirmed the reality of everything he could have seen in the Paths. With this in mind, Eren's laughter becomes something much more ominous. It becomes a sign of not only despair at losing Sasha but his resignation to the future.
Eren is put at the bottom of a dry well and will try to induce a transformation when given a signal. He repeatedly bites his hands, hoping the pain will cause the change.
He also gave his son the key to the basement which held all his information on the nation of Marley and his true objectives, before his son turned into a Pure Titan and ate him. This was Grisha's desire as it meant Eren inherited both the Attack Titan and Founding Titan powers.
If you remember Season 1 Episode 2, after the fall of Wall Maria, Eren wakes up with the vague memory that he'd met his father. His father had giving him a key, prepared an injection, and told him to look after Mikasa and Armin. That's also the scene where Eren ate his dad (he turned into a Titan from the injection).
Eren Yeager
This Titan was hidden within the royal Tybur family before Eren came into the picture and forcefully ingested the remains of the previous inheritor, Lara Tybur. As a result, he now houses the powers of the Founding Titan, Attack Titan, and War Hammer Titan.
Then, at that moment Eren, full of rage, hate and anger, screamed and “punched” the Titan's hand. Activating the Coordinate ability, a power that he did not know that he had, Eren seemingly started to gain control over the surrounding Titans and they proceeded to kill the Smiling Titan.
After closer inspection, and as the Titan gradually comes closer, they both realize it is Dina, the exact same Titan that devoured Eren's mother five years prior. As Dina approaches Eren and Mikasa, Hannes arrives to stop her.
Levi is the brother of Mikasa. Hughes is the father of Levi. Victoria is the daughter of Christa.
Remember the time where Levi kicked Eren right in the face and one of his teeth was gone? Soon, Hanji asked Eren to open his mouth and shocked that Eren's teeth were back.
Having to record lines on his own, he says he couldn't stop shedding tears while having to perform Eren's role. He talks about the deep connection he feels to the character and all the suffering Eren endured and how that impacted his performance.
A distraught Zeke watches Eren whisper in their father's ear, “You keep moving forward. Even if you die. Even after death.” Eren convinces his father in a moment of hesitation to kill the Reiss family.
Before Chapter 139 came out, Eren influencing the past and killing his mother was only a theory. However, now that the series is over, we have official word on exactly how Eren was involved at that point in the story. Eren sacrificed his mother for a better future for the world.
According to AOT's website, Eren Yeager is 19 years old in this final season. Mikasa Ackerman is also 19. An important thing that many AOT fans might already know is that the Ackermans meaning Levi and Mikasa are special, they do not undergo ageing like others do.
Rod Reiss (ロッド・レイス Roddo Reisu?), often publicly referred to as Lord Reiss (レイス卿 Reisu Kyō?), was the true king of the Walls from 845 to 850. He sought to return the stolen Founding Titan to the Reiss family, by having his daughter Historia eat Eren Yeager.
Titan shifting power is transmitted by the consumption of spinal fluid. The Titan failed to drink eren and thus never became one of the 9 Titans. Cucked over by plot.
Type of Villain
He was the father of Zeke and Eren Yeager. Born as an oppressed Eldian living in Marley, he joined a rebel organization known as the Eldian Restorationists, and subsequently used his son, Zeke as a spy to infiltrate the Marleyen military, along with his wife, Dina Fritz.
So If Eren was never eaten in Trost, he'd only have one leg, meaning he'd no longer be able to continue being a scout. Mikasa, being Mikasa, would likely resign from the scouts to take care of Eren, and Armin would probably also resign/be kicked out cos he would have kinda sorta lost his mind.
When Eren was eaten and swallowed by the Bearded Titan, he found himself in its stomach along with the bodies of its victims. His rage at the Titans caused him to burst out of the Bearded Titan's stomach by transforming himself into the mysterious Titan and going on a rampage against them.
When Season-3-Eren kissed Historia's hand, he saw Grisha's memory of his slaughter of the Reiss family, which Grisha did on Future Eren's orders, with Season-4-Eren present via Zeke's Founding Titan powers.
A Titan Shifter needs to draw blood in order to transform, and some, like Eren, bite into their hands. This can be a painful experience, but Shifters do not need to worry about these injuries because they will heal extremely quickly. When someone inherits one of the Nine Titans, they gain the ability to regenerate.