EreReiBert

EreReiBert is the poly ship between Reiner Braun, Bertolt Hoover and Eren Jaeger from the Attack on Titan fandom.

Canon
Before meeting Eren, Reiner and Bertolt were the closest of the trio. Throughout their childhood in Marley, Bertolt and Reiner trained together to become Marleyan warriors; they became quick friends due to Reiner's meek personality and Bertolt 's friendliness, and due to their shared goals: to return home and to bring glory to the shunned Eldians back in Marley.

After working together to breach a hole into the Wall Maria, they enrolled into the military and were placed in the 104th Training Corp. The two are almost always seen together as cadets, and were introduced together as partners.

During the Training Cadets arc, the both of them meet Eren, who went from bragging about killing titans to perceiving that becoming a skilled soldier wasn't an easy path. His frustration is clear not only about feeling ashamed about not understanding the basics of vertical maneuvering but that it would mean not being able to be on the frontlines to fulfill his concrete desire to exterminate the organisms he hated so much. Finally, Eren hears Marco’s advice to ask for help from other skilled cadets. And said cadets turn out to be Reiner and Bertholdt.

Back at the dorm, they have a proper moment to meet each other and Eren, Armin, Reiner, and Bertholdt talk about their past experiences discussing the terror of the titans, and the oldest duo question Eren and Armin on why they still want to be part of the army. The first parallel between Reiner and Eren is made explicit when they exchange similar determination gazes while spelling their main goals (for one, be able to return home, for the other, kill all titans). Reiner seemed to approve of Eren's determination and decided to help him.

They are shown to be great friends and listen to Eren's story about his mother's death, although it's not obvious, Reiner was guilty about what happened and forced himself to believe that he was a soldier, Bertolt is aware and is concerned for his friend's sanity. The guilt Reiner carried started affecting his grasp on reality, putting stress on his and Bertolt's relationship. He developed a dissociative-identity disorder (split-personality), where his "Soldier" personality started taking over his "Warrior" one.

It seemed that Reiner meant to help Eren genuinely, constantly partnering the younger on training exercises. During the three years of being a cadet, Eren built his concept of a soldier code by the influence of Reiner's words, since one time during training, Reiner sees Eren take a bad fall while training with his vertical maneuvering equipment and he tells Eren to take a break, but Eren is afraid to do so. Eren does not want to die without having accomplished anything and asks what he can do to be like Reiner. Reiner tells him to simply do what he needs to and keep moving forward. He says that he is certain Eren will exterminate all the Titans. His philosophy of "always moving forward" marks Eren's perception of life in general, becoming a shared motto later.

Despite Reiner's previously mentioned mental instability, Bertolt continued to trust his judgement and follow him. The duo show great concern for each other and work well together. The Scouts shelter at Utgard Castle against the moonlight titans, Reiner nearly gets killed by one of the titans reaching into the window, but is saved by Bertolt. They later work together to capture Eren and Ymir.

When Eren is on top of the Wall recovering from Castle Utgard's ordeal, he questions Ymir's condition and gives Reiner a hand up the Wall as Historia explains her true parentage. Helping Armin up as well, Eren goes to check on Reiner after hearing about how bad his arm was injured in the Castle; this, along with the moment that Reiner was almost killed by the Female Titan, causes Reiner to comment that he doesn’t expect that he'll live much longer and that they should keep fighting until the breach in Wall Maria is covered. After Bertholdt tells Reiner that they won't have to wait much longer and can return home soon, Hannes arrives with news. As Hange orders them to stay on standby in Trost District, Reiner goes to speak with Eren and Bertolt in private.

Reiner reveals himself as the Armored and reveals Bertholdt as the Colossal Titan. He then respectively tells Eren that they won’t attack the Walls if Eren returns to their homeland with them. Eren recalls Hange's theory about how Reiner and Bertholdt might be accomplices to Annie and tries to persuade Reiner that he's just tired and not thinking straight. In response to Eren's disbelief, Reiner removes the bandage on his arm and reveals that the wounds he had were regenerating. Mikasa attempts to protect Eren but Reiner and Bertholdt transform into their Titan forms and attack. Reiner grabs Eren while Bertholdt kidnaps Ymir and Eren, disgusted by his former friends, transforms himself.

Several hours later, Reiner and Bertolt transport Ymir and Eren to the Titan Forest, with them taking the opportunity to acquire Eren and Ymir's vertical maneuvering equipment while they were both unconscious. As Eren wakes up, Reiner and Bertolt exchange grim glances with him in light of the aftermath of Eren and Reiner's fight. Eren openly questions why his arms have been severed off, and Reiner says he did it due to the little time he had of capturing him. Eren acknowledges his defeat against Reiner, giving both Reiner and Bertolt a cold glance. Eren curses Reiner, saying who cares what he thinks, and Ymir questions Reiner and Bertolt's intentions of what they will do with them.

Eren demands Reiner to stop playing around and accuses him of playing the victim, asking Reiner and Bertolt whether he remembers telling them that a Titan ate his mother, and Bertolt vaguely says he felt sorry for him at the time. Eren expresses that they are murderers responsible for the genocide of innocent people. Reiner irritatedly says he already is aware, and Eren tells him to stop grieving as if he is a victim and that he is no longer human, being responsible for turning their world into a living hell. A frustrated Reiner asks what Eren wants from them then if he wants for him to apologize or atone for his actions or admit that killing is bad. He says that the person Eren once knew is dead and if it makes him feel any better, he can scream all he likes. Eren started to despise Reiner after he revealed himself as the Armored Titan. He started to only view Reiner as a despicable traitor to humanity you had no right at all to live. Eren wanted to make sure that he killed both Reiner and Bertholdt with the slowest gruesome pain they would ever feel. He felt that that would be the only death suited for disgusting traitors like them.

After Commander Erwin and the rest of the Survey Corp arrive to retake Eren, Reiner puts himself in a dangerous position by protecting Bertolt with his titan's hands instead of fighting off the Scouts and mindless titans. Even without Eren, Reiner continues to protect Bertolt as they get swarmed by titans. He realizes that this is the worst possible situation, thinking that Eren is the worst possible person to possess that power, knowing Eren very well, and how much determination Eren has, even more than him A while later, Reiner and Bertolt are seen on Wall Maria, appearing to have stayed the night on the Wall. They watch the sun set, waiting for the Survey Corps to arrive.

During the Return to Shiganshina arc, while on top of the Wall, to Eren's shock, Reiner emerges from the inside of the Wall and kills a Corps soldier before being attacked by Levi. As Reiner transforms into his Titan form, Eren is surprised again by the sudden appearance of an army of Titans on the outskirts of Shiganshina, with the Beast Titan leading them. Then Eren has to battle Reiner in the Armored Titan once more. Although he initially has the upper hand against Reiner, Eren is momentarily overpowered and pinned to the ground. He manages to regain control of the fight and throw Reiner off of him, and into an area where Hange's squad can attack. As Eren watches, Hange's squad blinds Reiner with their Thunder Spears before blowing open his Titan form's nape and apparently killing him.

When Reiner is defeated by the Scouts and is left at death's doorstep, Bertolt holds off Zeke's plan of bombing Shiganshina District with his titan transformation and chooses to save Reiner instead. This decision ended up having a fatal consequence for Bertolt, who, because he failed to kill the Scouts sooner, ended up captured and eaten by Armin's mindless titan. His decision to put Reiner's survival above Zeke cost Bertolt's his life and the mission's success.

A time skip of four years follows, turning the point of view to adult Reiner and his life in Marley. Reiner still thinks about Bertolt and the other fallen Marleyan Warriors. Reiner might be unaware that Bertolt was devoured. Some of his flashbacks focus on Eren of all people, one of them right before actual Reiner attempts against his life (being interrupted by Falco's outside complaining in the real-world). When Reiner eventually talks or remembers the old times in Paradis with the 104th cadets, it's a mix of longing, regret, and sadness.

When Eren and Reiner meet again four years later, Eren's hatred towards Reiner seems to have gone down to some point, expressing to Reiner that it is good that he had managed to return to his hometown. In return, Reiner was shocked by Eren's return to him and could barely say a word to him. Eren expresses sympathy towards Reiner after learning the truth about Reiner's mission within the Walls and the world's hatred towards Eldians and experiencing the same infiltration mission within Marley that Reiner carried out years before. Eren admits he and Reiner are the same, driven by freedom for their people and manipulated by corrupt leaders for the actions of their ancestors. Eren even admits his own anger towards Reiner and Bertolt was a bit too much due to him not knowing their reasons why. Eren looks pained but genuinely concerned about Reiner, sincerely just looking for an answer to his inner conflictual question. Thanks to Reiner's response, Eren states that they are the same, as two sides of a coin.

Eren starts a raid in Liberio, saying that he will "keep moving forward". Despite not being interested in killing Reiner, Eren has his agenda of destruction clear and Willy Tybur declares war on Paradis Island. Later on, Reiner is urged by Falco and Gabi to take part in the titan battle in order to rescue the Jaw Titan from being consumed by Eren, who curiously seemed to forget the matter at hand to run for a new match with his long-term arch-enemy of sorts. As Reiner showed no big resistance, Eren retreats, giving one last sad glance at Reiner while promising to see him again soon.

And, indeed, they see each other once again during the War for Paradis arc, where they have their fourth fight. Reiner silently admonishes Eren for continuing to fight and wishes he would just give up his efforts as both of them are doomed to die in a few years' time; he then tries to devour Eren, but is stopped as Eren manages to get a hold of his Titan's head and begins to separate it from the neck by breaking his jaw. As Reiner endeavors to break free from Eren's grip, he is knocked off of his adversary by a projectile thrown by the Beast Titan.

Some time later, Reiner allies with the Alliance, and they go to meet with and stop Eren's plan. En route to Eren, Reiner participates in a meeting to discuss how to best stop him. During the discussion, Reiner recalls Eren's claim in Liberio that he and Reiner are no different from each other. Reiner suggests that Eren might truly want them to stop him, showing once again how well he understands Eren. Reiner suggests that the pain of slaughtering humanity might be too much for Eren, and that he is waiting for someone to either take the Founder away from him or stop him. Reiner is interrupted when Eren suddenly pulls the group into Paths to speak with them. He tells them that they will have to kill him if they want to stop the Rumbling, exactly what Reiner guessed.

When they reach Eren, Reiner jumps from the flying boat they were in with his comrades and uses his maneuvering gear to get closer to Eren before transforming into his Titan form. Before the group can make any progress, he meets with Bertolt's Colossus Titan, which is being manipulated by Eren, and which appears and grabs Reiner. It attempts to devour him, but Reiner is rescued from his Titan's nape by Jean at the last second. The Colossus Titan throws Reiner's Titan at the group, and the impact knocks them all from Eren's Titan. Reiner and Jean's maneuvering equipment are busted and they are left stranded, hanging from Eren's Titan. Reiner tries to convince Jean to let him go so he can transform again, but Jean points out that he will only be crushed by the Colossus Titans beneath Eren. As the Nine Titans of the past begin to attack, the group is rescued by the arrival of Falco, who has learned to fly with his Jaw Titan.

Following the battle and Eren's death, the Power of the Titans is eliminated from the world and all of the Eldians return to their human forms. Recovering his memories of his final conversation with Eren, Reiner mourns for his death.

Fanon
is a rare poly ship within the Attack on Titan fandom. It's overshadowed by more popular ships, including two of the trio, such as the most popular one, ReiBertAni. Most EreReiBert fans recall the moment where Eren finds out that both Reiner and Bertolt are the Armored and Colossal Titan, respectively, as one of the most iconic of the whole series. And the sheer pain this caused to Eren, as he cried while transforming after the revelation, just makes their relationship all the more tragic. Although the first one to die of the trio is Bertolt, he keeps making appearances in relation to this ship, and the relationship Eren and Reiner keep developing keeps this ship's interactions alive.

Fandom
FAN FICTION

Variations

 * EreRei refers to the ship between Eren Jaeger and Reiner Braun
 * ReiBert refers to the ship between Bertolt Hoover and Reiner Braun
 * EreBeru refers to the ship between Eren Jaeger and Bertolt Hoover