|It's like a strike of lightning. Hence the name, "Thunder Spear."|
|— Hange Zoë explains how their new weapon came to be named|
The Beast Titan sends its smaller Titans in to kill off the Scout Regiment's horses while the larger Titans form a semi-circle in front of the Wall to cut off escape from Shiganshina District. To protect the horses, Erwin Smith has the majority of Scouts defend the gate, and uses Eren Jaeger as bait to lure away Reiner Braun's Armored Titan.
The Scouts at the gate struggle against the Titans due to the losses they have suffered over recent months, but inside Shiganshina, Eren creates an opportunity for the Scouts to use their new Thunder Spear weapons against the Armored Titan. Hange Squad and Levi Squad succeed in blinding the Armored Titan and destroying its nape.
The Beast Titan and its companion Titans stand outside Shiganshina District as the Scout Regiment awaits them on top of the Wall. Behind the Scouts, Reiner Braun hardens the fingers and toes of his Armored Titan to begin climbing the Wall. Erwin orders the Scouts to avoid fighting the Armored Titan and to stay away from it.
A little further down the Wall, Eren Jaeger asks why Erwin does not give the order to attack. Hange Zoë replies that he is watching the enemy's movements, because Reiner and the others clearly have something prepared for them.
Meanwhile, Erwin notices that there is a quadruped type of Titan next to the Beast Titan that is carrying some sort of cargo on a makeshift saddle on its back. It is not one of the newly transformed Titans. He suspects that it might have been the enemy's scout. It could have seen the Scout Regiment's approach and reported it to Reiner, which would mean that it is also an Intelligent Titan. Erwin does not want to discount the possibility that there could be even more.
The Beast Titan roars, and the smaller two- to three-meter Titans to either side of it charge in towards the Wall. Erwin realizes that the Titans intend to go after the horses first, which are trapped on the Titan side of the Wall. Their enemy's primary objective is to capture Eren, but they can do that by taking away the Scouts' only means of escape. Wall Maria is still deep in Titan territory, so the Scouts have no means to get back or resupply without horses. Then the Titans can simply wait them out until the Scouts are too weak to fight back. The fact that the larger Titans are standing in formation in a semi-circle in front of the Wall is proof that their purpose is to cage in the Scouts.
Armin Arlelt informs Erwin that the Armored Titan is getting close and they still do not know where Bertholdt Hoover is. Erwin acknowledges this, and concludes that at this point in time, his worst fear is that the Scouts will lose their horses, so he orders Dirk Squad and Marlene Squad to join Klaus Squad at the gate. He then instructs Levi Squad and Hange Squad to take down the Armored Titan. They are to use their Thunder Spears at their discretion.
As the Scouts move to carry out their orders, Erwin calls back Levi and Armin. He asks Levi to stay to protect the horses rather than Eren, and to take down the Beast Titan when the opportunity comes. Levi understands and jumps down to join the other squads at the gate. Erwin then tells Armin his plan for the Armored Titan.
The Armored Titan reaches the top of the Wall and oversees the smaller Titans fighting with the Scout Regiment. Reiner notices that the horses are all tethered in one place, and figures it will be easy to kill them before making a break for it. The flesh inside his Titan removes Levi's blade from his neck and Reiner realizes if he had been any slower moving his consciousness from his head to his body, he would have died. He then spots Erwin standing alone and vulnerable on the Wall, but tells himself not to get distracted.
Behind him, there is the sudden flash of a Titan transformation and he sees Eren's Titan standing in the streets below. Eren then runs deeper into Shiganshina District, forcing Reiner to choose between Eren possibly escaping over the southern Wall of Shiganshina or taking out the horses. As a Titan, Eren could escape all the way to Trost District regardless of whether he has a horse. Even if the Warriors slaughted the entire Scout Regiment, it would still be a loss if they let someone who mastered hardening in two months back inside the Walls.
Reiner comes to the conclusion this is a feint, because if Eren was truly trying to escape, he would not have transformed until he used his omni-directional mobility gear to scale the Wall. By transforming early, the Scouts are forcing Reiner to choose between the horses and Eren. Reiner is frustrated and slides back down the Wall to go after Eren.
Minutes before, Armin relayed Erwin's instructions to use Eren as bait to Hange. Mikasa was skeptical, but Hange said that if Reiner ignored Eren, Eren could circle around behind the enemy Titans and attack the Beast Titan, forming a pincer with Levi and the rest of the Scouts. Even if Reiner did not follow the plan, it would confuse the enemy enough for them to break ranks. Hange agreed to follow Erwin's plan, but before she and the rest of Levi Squad went to execute it, Armin reminded them that Bertholdt is still hiding somewhere. To avoid Eren losing like the last time he fought the Armored Titan, when the Colossal Titan fell on him, Armin suggested they fight away from the Walls.
As Eren waits for Reiner to meet up with him in the middle of Shiganshina, he reminds himself that even if it was a fluke, he beat Reiner before. He is certain he can defeat him one-on-one. Eren hardens the backs of the fingers on his Titan's hands and Reiner charges towards him. The two tussle and Eren draws strength from the fact they are fighting in the town he once called home. He manages to strike his hardened fist into the side of Reiner's head, cracking his armor and knocking him to the ground.
Outside Shiganshina, the new recruits of Klaus Squad move the horses to better protect them. Floch is visibly upset as he asks Marlo Freudenberg where to put them, and Marlo replies that they are supposed to spread them out. Overhead, the veteran Scouts move to fight off the Titans. Marlo gets his first look at a Titan as Levi swings through to kill the two chasing the recruits.
Seeing that the recruits are safe, Levi yells at the veterans to clean up the small Titans before the Beast Titan makes another move. As he looks over the battlefield, he finds it pathetic. Up on the Wall above, Erwin is of a similar mind. He sees that the Scouts are struggling with three- to four-meter Titans and there are too many casualties. They have lost too many veteran soldiers, but without their sacrifices, the Scouts would never have made it this far.
Erwin thinks back when he was a cadet and told others about his father's theory. He thought that once he was a Scout, he would prove it, but after he joined the Scouts he stopped talking about it. Unlike the other Scouts, who were fighting for a greater purpose, he realized that he was only fighting for himself, for his specific dream. Before he knew it, he was in a leadership position where he had to give orders and inspire others, so he had to fool his comrades and fool himself into making sacrifices. But still, he finds himself drawn to the basement. Even if this plan fails, he might be able to reach it before he dies and learn the truth that Grisha Jaeger left behind.
Eren and Reiner continue fighting, with Eren clearly holding the upper hand. By focusing all his hardening on one spot, Eren finds that it gets even stronger. Since Reiner's armor is spread across his whole body, Eren can now smash it like thin ice. But Eren gets overconfident and misjudges Reiner's counterattack. Reiner grabs Eren's Titan by the ankle and swings him overhead into a building.
Seeing that Eren appears to be in distress, Mikasa Ackermann wants to help, but Hange instructs her to wait for Eren to give them an opening.
Prior to the Scout Regiment setting out for Shiganshina, Hange had a new weapon developed, the Thunder Spear, using technology that had been kept hidden by the Interior Police. She wanted something that could be used against the Armored Titan since their blades do not work and they do not want to rely solely on Eren's Titan. Though plugging the Wall is important, they have to stop Reiner and Bertholdt who are responsible for breaking the Wall in the first place.
In the present, Eren and Reiner grapple with each other and Eren manages to throw Reiner off of him. As Reiner realizes that he cannot take Eren on by himself, Hange leads her squad and Levi's to attack the Armored Titan. Reiner is surprised, not expecting that they can actually damage him, when Hange and Mikasa fly towards him armed with their new Thunder Spears. The rodlike projectiles impale Reiner in the eyes and then explode, blinding him.
From behind, the rest of Hange and Levi Squads attack, firing their Thunder Spears into the Armored Titan's back and disengaging before they can get caught up in the explosion. Jean Kirschtein shouts that it worked, the armor around Reiner's nape is peeling off. Hange calls for them to attack again to finish him off, but Conny Springer and Sasha Braus hesitate, realizing that they will have to kill a former comrade. Jean rallies them and the three move in to attack with the rest of the Scouts.
Multiple Thunder Spears pierce the Armored Titan and Reiner panics just before they explode.
Currently Publicly Available Information
A weapon developed to combat the stout defense of the Armored Titan using technology formerly kept secret by the Interior Police. Though challenging to wield, it can deliver a concentrated blow comparable to a strike of lightning.