|I wish to make certain of something, Mr. Jaeger. As a soldier, can you continue to serve humanity by controlling your Titan ability?|
|— Dhalis to Eren Jaeger|
Dhalis Zachary (ダリス・ザックレー Darisu Zakkurē?) was the premier of the three regiments of the military (三兵団総統 San Heidan Sōtō?, also translated as "Commander-in-Chief of the Three Regiments"), and as such oversaw the Scout Regiment, the Garrison Regiment, and the Military Police Regiment.
Zachary 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 gave him a presence uncommon for a man of his rank. Zachary'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 Dawk, Erwin Smith, and Dot Pyxis. Over this he wore a brown trench coat that had a black shield emblem with a white boarder and cross.
When he was first introduced, Zachary 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 indicated that Zachary 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.
However, after Zachary assisted in the revolution against the monarchy he showed 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 helped humanity or not. Ultimately, he was willing to admit that he valued his own life more than humanity.
Zachary showed a demented, sociopathic side to his personality when he had set up a torture machine and subjected an official to inhumane torture, laughing while forcing him to drink his own urine and calling that torture machine the finest work of art. In the end, his only interest was his own desire to humiliate the monarchy.
Zachary first appears when he arrives at the court place when Eren Jaeger is put on trial. At the courtroom, 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 Scout Regiment, or he will go the Military Police Regiment and be killed.
Zachary calms Pastor Nick down after he called for Eren's immediate destruction and then offers Erwin the chance to speak. The latter expresses his plan to use Eren's powers to retake the Wall Maria. A merchant and Levi then argue about the sealing of the gates. Nick interrupts again and begins arguing with the merchant, prompting another call for order from Zachary.
Zachary asks if Eren can use his powers for good, Eren replies yes and Zachary counters that Eren reportedly attacked Mikasa Ackermann, another soldier. She reluctantly admits that he did attack her but also requests that it be taken into consideration that Eren saved her life twice before that.
Nile disagrees with this by citing an incident from Eren's past where he stabbed two robbers. Eren begins to get angry and is pointed guns at by the Military Police but Levi arrives and begins to beat him. Erwin then offers a proposition to Zachary: the Scout Regiment will take Eren and assess his usefulness to humanity and if anything goes wrong, Levi will kill him. Zachary agrees with this deal and announces that Eren will join the Scout Regiment and return to trial after his ability has been assessed.
Zachary takes part in Erwin Smith and Dot Pyxis's plan to overthrow the government. After the government officials, believing that the Walls have been breached, demand that no refugees be allowed into Sina, Zachary 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 has fallen and the royal capitals administrative district have been conquered, Zachary and Erwin board a carriage. Erwin voices his doubts that their decision to overthrow the government was best for humanity, and Zachary 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 from him.
Soon after, he is seen torturing Aurille by hanging him upside down and forcing him to drink his own urine. As Zachary 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 Zachary's memories to the point where he could not remember how to defecate, but Zachary silences him by plugging the device's tube into the official's mouth as he lets out a burst of laughter.
After the attack on Orvud District, Zachary and the commanders of the various military branches crown 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.
Zachary oversees a meeting with the military's other commanders to decide what to do with the Titan injection that Kenny Ackermann gave to Levi. With no way to properly analyze the contents of the bottle, the brass decides to entrust it to Levi.
As Armin Arlelt explains his plan for victory against the Colossal Titan to Eren, Zachary sits with the other military leaders drinking tea and worrying if the operation to retake Wall Maria and humanity's land will be successful.
As the military leaders wait for the Scouts' return, Nile tells them about a theory of Erwin's that he had laughed at when they were youths, and Zachary encourages him to apologize to Erwin once he has returned. Shortly afterward, they are informed by Anka that the Scouts have returned.
After the Scouts' return, Zachary 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, Zachary attends another military meeting to discuss Zeke Jaeger'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 Scouts. Zachary 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.
Zachary 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 flying boat which uses iceburst stone as fuel.
Zachary returns to the military's headquarters, where he has a meeting with Mikasa Ackermann and Armin Arlelt. Apologizing for his tardiness, Zachary tells the two that they will not be able to visit Eren. 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 interact with him. Armin tries to convince Zachary to change his mind, but Zachary makes it clear that they will not be seeing Eren any time soon.
Zachary sees that Armin and Mikasa have noticed his custom-made chair in the corner of his office and waves it off, explaining that there was nowhere else to put it. Zachary stands by his decision and ends the meeting, sending Armin and Mikasa away as three members of the Military Police Regiment arrive to see him. During the meeting a bomb in his chair goes off, killing him and destroying his office. His dismembered corpse lands outside the building in full view of the protesters.
As commander-in-chief, he was the highest authority within the military structure. The three military divisions, the Garrison, the Military Police, and the Scout Regiment 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.