|There is no such thing as truth in this world. That is our reality. Anyone can become a god or a devil. All it takes is for someone to claim that to be the truth.|
|— Kruger about the legitimacy of Ymir Fritz's story|
Eren Kruger (エレン・クルーガー Eren Kurūgā?) was an Eldian spy posing as a Marleyan soldier. To his comrades in the Eldia Restorationists, he was known as the Owl (フクロウ Fukurō?) and he was secretly an inheritor of one of the nine Titans.
Kruger was a fairly large, well-built, older man. He had shaggy dark hair with gray in it which he kept combed to the side. Kruger had a very slender face and pronounced cheekbones and can usually be seen wearing the standard uniform for Marleyan soldiers, although he only wears his uniform's hat when he is facing civilians. He also heavily resembled Eren Yeager as a young child.
As a Titan, Kruger's form shared some features with Grisha and Eren Yeager's Titan forms due to them all being of the same type; he had sunken eye sockets, was very muscular, and had long dark hair. However, his Titan form also shared some unique facial characteristics with his human form, such as his pronounced cheekbones.
Kruger appeared to be unconcerned with the well-being of others and never showed his emotions. After finding Grisha and Fay Yeager outside of their Internment Zone, he felt no qualms in punishing Grisha physically. He again seemed to show a lack of empathy when the Yeagers learned of Fay's death, remaining stone-faced at the sight of their sorrow. However, it can be indicated that, due to his job as a mole, he had to behave like that in order keep his identity from being exposed.
Kruger was born to an Eldian family living in Marley. His father had joined an Eldian revolutionary army led by the remnants of the royal Fritz family who remained on the mainland. Unfortunately, the army was very ineffective, and its members, including Kruger's father, were captured and burned alive by the Public Security Authorities as he hid in a closet. Some time later, Kruger was able to join the Public Security Authorities as a spy thanks to an Eldian doctor who was able to fake his blood tests as he had done for himself some time earlier. As a spy in the military, Kruger would refer to himself in correspondence with the Eldians as "the Owl", all while spending his military career turning thousands of Eldians into Titans over the years in order to hide his identity.While spending his downtime watching blimps with one of his fellow soldiers, Kruger caught sight of Grisha and Fay Yeager following the blimp. Observing their armbands, Kruger deduced that they are from the Liberio Internment Zone. Because they had left their Internment Zone without permission, Kruger offered them a choice between hard labor or "physical punishment". Grisha chose to take both his and Fay's punishment, and Kruger proceeded to savagely beat him. Afterwards, however, Kruger showed a hint of compassion, allowing Grisha to stay with him to watch the blimp for a while longer. Kruger accompanied his fellow soldier to inform the Yeagers of Fay's death and observed quietly as they grieve for Fay.
Thirteen years after inheriting his power, when the "Curse of Ymir" was beginning to take hold of his health, Kruger was present when Grisha was tortured by the Public Security Authorities. He asked if he confessed the Owl's identity, and Grisha assured he did not know. Kruger announced the boat that will send the Restorationists to Paradis was ready.During the operation, he calmly watched the Restorationists being turned into mindless Titans and chase after their comrade. As it was Dina Yeager's turn to be transformed, Kruger violently silenced a yelling Grisha. When Gross was about to throw Grisha off the Wall, Kruger suddenly pushed his comrade and revealed to a shocked Grisha that he was the Owl. While mutilating his hand, he taught Grisha how to use the power of the Titans before, in his Titan form, destroying the Marleyan steamboat and slaughtering all its soldiers.
He then set Grisha free and answered all the questions of the latter, justifying his deeds and telling him about his life. Before letting a determined Grisha inherit his ability in order to fulfill the Eldia Restorationists goal, Kruger revealed him the name of the Titan he would become and explained the history of the Founding Titan and King Fritz's vow with the Founding Titan renouncing all war. As he prepares to inject Grisha with a Titan serum, he urges him to find a family and complete his mission for the sake of Armin and Mikasa. Grisha is confused by these names, and Kruger admits that he does not know whose memories he is seeing.