After an epic third season, fans have been highly anticipating Season 4 of Attack on Titan, which arrives this December. Season 3 was split into two parts. The first aired in 2018 and focussed largely on Eren Jeager and the rest of the Survey Corps opposing the government, who were hiding many secrets about their world. As it turned out, they had spent the last century using any means necessary to keep people ignorant within the confines of the walls.

This revelation caused those in charge to permanently make an enemy out of the Survey Crops, which wasn't helped by them demanding custody of Eren, a Titan Shifter, and Historia, the rightful heiress to the throne. While the series up until this point has focused on the battle between humans and Titans, this arc forced the main characters to go up against other humans within the walls.

Season 3, Part 2 concluded in 2019 and focused on the mission to retake Wall Maria -- a major attempt to turn the tides of the war in humanity's favor. Here, the Survey Corps once again faced-off against Titans, including the Colossal Titan, the Armored Titan and the Beast Titan, all monstrous and formidable opponents. However, the price for taking back Wall Maria was high as almost the entirety of the Survey Corps were completely wiped out.

At the very least, the characters were finally able to uncover the long-teased mystery of what secrets lay in the Jeager family's basement. But the Scouts found just as many answers as they did problems there.

In the lead-up to the fourth and final season, here is a refresher of the key plot points that are sure to make a reappearance when the Attack on Titan anime returns.

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Eren Vs. Zeke

Eren meets Zeke on the Cart Titan

Although Zeke's identity isn't revealed until the third season, the series linked Zeke to Eren as a key antagonist early on. In Season 3, we learned that he was Eren's half-brother, the son of Grisha Jeager and Dina Frtiz, and that he wanted to save Eren, claiming that Grisha brainwashed him. Other than that, he's still very much a mystery. It is unknown how or when he obtained the powers of the Beast Titan or the details of his life after turning his parents in to obtain punishment for being part of the Eldian Restorationists in the world beyond the Walls.

The last we saw of Zeke, he appeared to be dead set in his beliefs, and vowed to one day return to save Eren. It can be inferred that Zeke has dealt with many hardships in his life and that there is more to his grudge against Grisha than we know. Many of the key incidents in Attack on Titan have been a chain of events set off by Zeke, so it is only fitting that the show would be leading to a final confrontation between Eren and Zeke in Season 4.

Armin is Now the Colossal Titan

Armin Arlert surrounded by Connie Springer, Eren Jeager, and Mikasa Ackerman in Attack on Titan

Immediately after the fight against Zeke, Reiner and Bertoldt, both Armin and Erwin were left with ghastly injuries, clinging to life. Levi was forced to choose which one to save by turning them into a Titan with a spinal fluid injection. While his initial choice was Erwin, the Commander thought his time to be over and wished for Levi to save Armin, which he did. Armin was turned into a Titan and ate Bertoldt, gaining the powers of the Colossal Titan.

While Erwin did all that he could and set the foundations for Armin to take over, not all were convinced that saving Armin was the right choice. Floch, in particular, thought that Levi made a mistake, voicing his concern that Armin was unqualified next to Erwin, who aided the Survey Corps in making it this far.

Armin also questioned whether Levi made the right decision, feeling unworthy of being chosen. Nevertheless, Armin is now in a position of leadership and has obtained great power. He must learn to step into this new role and work with Hange, the new Commander, to lead the others to freedom.

Related: Attack on Titan: Everything We Know About Zeke From the Anime

Unlocking Eren's True Power Requires Historia's Blood

Since the Season 2 finale, Eren has struggled to properly use a power that allows him to control Titans with just his voice. In the Season 3 finale, he figured out why that was. Eren was only able to use this ability in Season 2 after making contact with the Titan form of Dina Fritz, a person of royal blood. To replicate those results, Eren believes that he needs to touch a member of the royal family when they are in Titan form to fully utilize the Founding Titan's powers.

While only someone of royal blood can wield the true power of the Founding Titan, they become caged by the first King's ideals and refuse to fight. In fear that this knowledge will put Historia's life in danger, Eren chose not to say anything at all, but he might have to go back on this decision in the coming season.

The Curse of Ymir

Ymir Fritz

The founder of the Nine Titans was Ymir Fritz who lived for 13 years after obtaining her Titan powers. Her single power was split into the Nine Titans, which have been passed on to the Eldian people for 2,000 years. Using that logic, it is believed that the ones who inherit the power of one of the Nine Titans will also die in 13 years. This means that Eren, Armin, Reiner, Annie and Zeke have a finite number of years left -- even less so with the final season taking place several years after Season 3's finale.

Eren and Co. Have New Enemies

In addition to fighting Titans, Season 3 revealed that the ones behind the creation of the monsters are other humans. Everyone within the walls is part of a race known as the Subjects of Ymir. These Subjects have the ability to be activated as Titans through the injection of Titan spinal fluid. While we have seen a civilization who despises the Subjects of Ymir through Grisha's memories, Hange Zoe states during the meeting in Season 3's "Attack Titan" that the entire world may view them in the same light, making every human outside the walls their enemy as they try to eradicate the Subjects of Ymir in fear that they will one day rule the world.

Before this revelation, the characters of Attack on Titan believed that freedom laid beyond the walls after the annihilation of all Titans. Now, they know who their true enemy is, and despite the season ending with them finally making it to the sea they longed to see, Eren did not enjoy it; instead, questioning if they will ever obtain true freedom.

Whatever new challenges lie ahead, Attack on Titan Season 4 will premiere on December 7.

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