|Whether this revolution is good or bad for humanity is of no interest to me. I suppose that makes me quite the villain. But...you're no different, are you?|
|— Zackly reveals his true feelings|
Darius Zackly (ダリス・ザックレー Darisu Zakkurē?) was the general of the three military branches (三兵団総統 San Heidan Sōtō?, also translated as "Commander-in-Chief of the Three Military Branches"): the Survey Corps, the Garrison, and the Military Police Brigade.
Zackly had the typical appearance of an old man. His eyes were sunken and tired-looking, he wore glasses, he had noticeable wrinkles on his face, and his hair was receded and gray. He also had a gray scruffy looking full beard and mustache. In addition, he was rather short which gives him a presence uncommon for a man of his rank. Zackly's casual attire consisted of a plain white shirt with normal dark colored pants. In a more formal setting, he added a bolo tie, much like the three commanders under him, Nile Dok, Erwin Smith, and Dot Pixis. Over this, he wore a brown trench coat that had a black shield emblem with a white border and cross.
When he was first introduced, Zackly was said to be a strict military leader who was only concerned with the best interests of humanity. As the head of the entire military, his priorities were said to lie within what is best for all of humanity. Only after being logically convinced of Eren's usefulness did he pardon him. At this time he appeared to take most things lightly, as if he had experienced them previously. During the trial of Eren, he wore simple clothes and conducted the trial without any drama or passion. Similarly, he overthrew the monarchy with an incredibly casual demeanor. This indicates that Zackly had no time for drama and was solely focused on carrying out his judgments. He remained ever serious but at the same time appeared tired as if his age was catching up to him.
According to Armin, Zackly was among the people capable of abandoning their humanity to outdo the Titans as well as having the guts to also abandon things important to them in order to change something in the world, along with Erwin Smith, Ian Dietrich, and Dot Pixis.
However, after Zackly assisted in the revolution against the monarchy he shows a completely different personality. He noted to Erwin that his only interest in participating was due to an intense and long-standing hatred of those in charge. He took great delight in seeing their fear when they fell from power. In direct contrast to the idea that he acted in the best interest of humanity, he told Erwin that he did not care if the revolution helps humanity or not. His only interest was his own desire to humiliate the monarchy, such that he set up a torture machine that fed one of them their own feces and called it a beautiful work of art, showing a demented and psychopathic side to him. Ultimately, he was willing to admit that he valued his own life more than humanity.
Zackly first appears when Eren Yeager is put on trial. He confirms who Eren is and then announces that the sole right of judgment rests with himself. Eren will either survive and go with the Survey Corps, or he will go the Military Police Brigade and be killed. After Nile Dok, Commander of the Military Police, advocates for Eren's death, Zackly calms Minister Nick down after he calls for Eren's immediate destruction and offers Erwin the chance to speak. Erwin calmly announces that with Eren they can retake Wall Maria, which should be the top priority of humanity. After one of the merchants in attendance advocates destroying the Walls' gates, prompting another outburst from Nick, Zackly must calm the minister down again.
When Eren argues that he can use his powers for good, Zackly points out that Eren reportedly attacked Mikasa Ackerman, another soldier. After Levi beats Eren into submission in the middle of the hearing, Erwin proposes that the Survey Corps take Eren and assess his usefulness to humanity, with Levi prepared to kill him if anything goes wrong. Zackly agrees with this deal and announces that Eren will join the Survey Corps and return to trial after his ability has been assessed.
Zackly appears again during the trial of Erwin Smith in the King's throne room. After the government officials, believing that the Walls have been breached, demand that no refugees be allowed into Sheena, Zackly barges in and reveals that the breach of Wall Rose was a ruse. Erwin is released and the officials are then taken into custody for valuing their wealth over the lives of the people.
After announcing to the people that the old regime had fallen and the royal capitals administrative district had been conquered, Zackly and Erwin board a carriage. Erwin voices that it may have better to leave all authority to the former royal capital and send his friends and himself to his death if it meant that half of humanity would survive, as opposed to all of humanity dying to the Titans. Zackly comments that with the current state of things, death may have been a preferable option. He goes on to reveal that he himself has long since despised the government, and has waited his entire life for this day. He appears rather amused as he recalls the hysteria that the arrested officials displayed, remarking that he has been contriving various methods of humiliating them. He claims that he does not care whether or not the revolution benefits humanity, acknowledging that this puts his morality into question, though he believes Erwin is no different than him.
Soon after, he is seen torturing an official by hanging him upside down and forcing him to drink his own urine. As Zackly describes the different ways he plans to torture the official, he praises the torture device as the greatest work of art ever conceived. The official taunts him, saying that he has slave's blood and the official's royal blood will enable him to erase Zackly's memories to the point where he could not remember how to defecate, but Zackly silences him by plugging the device's tube into the official's mouth as he lets out a burst of laughter.
After the battle with Rod Reiss and attack on Orvud District, Zackly is among the military branch leaders, Nile Dok, Erwin Smith, and Dot Pixis, when he crowns the true heir to the throne, Historia Reiss, as the new queen of the Walls. The officials then kneel in front of Historia and she bows to them before turning to the crowd and offering her heart in a salute as they cheer.
As Armin Arlert explains his plan for victory against the Colossus Titan to Eren, Zackly sits with the other military leaders drinking tea and worrying if the operation to retake Wall Maria and humanity's land will be successful.
After the Survey Corps' return, Zackly is one of three military commanders, including Historia, to preside over a meeting to debrief them on the military's plans moving forward.
In the year 851, Zackly attends another military meeting to discuss Zeke Yeager's proposition and terms of an alliance. Many officials outcry about the ridiculousness of making a deal with the man who had nearly annihilated the Survey Corps. Zackly admits, however, that the proposal is consistent with his previous goal to retake the Founding Titan, and only represents a change of tactics after his defeat in battle.
Zackly welcomes Kiyomi Azumabito who has arrived to Paradis. As she congratulates Eldia on their recent victory on Marley, he gives credits to the bonds between their two countries and thanks her for coming in such a dangerous place, apologizing that he cannot give her a real welcome party. Kiyomi then tells him about what Hizuru gave to the island, a plane which uses iceburst stone as fuel.
Zackly returns to the picketed military's headquarters, where he has a meeting with Mikasa Ackerman and Armin Arlert. Zackly begins the meeting by apologizing for taking so long to see them, before bluntly telling them that they will not be able to visit Eren in his cell. He explains that due to the recent revelations that Eren had been meeting secretly with Yelena, and his refusal to answer the military's questions, it has been deemed likely that he is being controlled by Zeke, and is too dangerous for anyone to be allowed near him. Armin tries to convince Zackly to change his mind, but Zackly makes it clear that they will not be seeing Eren any time soon.
While there, Armin and Mikasa notice the chair that Zackly had built to torture one of the old military officials sitting in the corner of his office. He waves it off, explaining that there was nowhere else to put it so he had some recruits bring it here. Zackly stands by his decision and ends the meeting, sending Armin and Mikasa away. After they leave, three members of the Military Police Brigade arrive for a meeting with Zackly. As they enter, a bomb placed in his torture device goes off, killing Zackly and destroying his office. His dismembered corpse lands outside the building in full view of the protesters.
It is later revealed he was assassinated by rebels who believe the military was moving forward with a plan to have someone more convenient to them inherit the Founding Titan.
As commander-in-chief he was the highest authority within the military structure. The three military divisions, the Garrison, the Military Police, and the Survey Corps were all officially under his command, despite having their own leaders. In matters of military law, he was the sole decision maker that could not be argued against. Within the context of a Military Court, he had the power to condemn the defendant to death if he chose to.
Darius Zackly's statistics :