|The power of the Titans is absolute, and it must always remain that way.|
|— Magath worries for his country|
Theo Magath (テオ・マガト Teo Magato?) is the commander (隊長 Taichō?) of the Eldian Unit of the Marleyan military. He led the Eldian Warriors in the Marley Mid-East War against the Mid-East Allied Forces, playing a key role in Marley's victory.
Magath is an older man with gray eyes and a thin beard, mustache, and black hair with a short buzz cut. He has visible wrinkles from age but an overall healthy build and appearance. Like his fellow soldiers, he wears the standard Marleyan soldier uniform consisting of a light jacket and pants with a black clip at the collar, supply packs on the hip, suspender straps, a hard hat with a black stripe around it, and tall combat boots.
Magath is extremely dutiful, and most of his personality and choices revolve around what he believed was his duty as a soldier of Marley. Even though he, as a typical Marleyan, is prejudiced against Eldians, valuing the lives of the Marleyans above the Eldians and being angered when one questions his orders, he is willing to put his opinion aside and let the Eldians under his command speak, in case they might have something useful to add to the current situation, such as Colt Grice and Zeke Jaeger.
Many of his decisions make him appear as though he considers the Eldians under him as expendable pawns and is uncaring towards their lives, such as deciding to sacrifice 800 Eldian soldiers to destroy the anti-Titan artillery, while keeping two holders of the power of the Titans and the Warrior candidates safe. However, he mostly went with this course of action because it is most beneficial to Marley, as he wanted to keep Warriors, as well as the Warrior candidates, out of harm's way since most of his nation's might comes from the Titans, being aware of the other nations' technological superiority.
Magath has acted as the chief overseer of the Warrior unit since its outset, evaluating the performances of each individual Warrior candidate and selecting the top performers to be inheritors of the power of the Titans. By the early 840s, Magath had achieved the rank of commander.
Magath was among those deliberating who the next inheritors from the most promising of candidates should be; he would ultimately select Annie Leonhart, Bertholdt Hoover, Marcel Galliard, Pieck and Reiner Braun to receive the Female, Colossal, Jaw, Cart and Armored Titans. In the year 843, during the final battles between Marley and an enemy nation, Magath was among those who witnessed the enemy's destruction at the hands of the newly trained Titan Warriors. Magath admitted that while they were more effective than their predecessors, he expressed some resistance to the decision of entrusting the upcoming Paradis Island Operation to mere children.
About four years after the failed Paradis Island Operation, Magath leads an 800-man Eldian unit against the Mid-East Allied Forces at the battle of Fort Slava. When the Eldian unit's advance is halted to by the fort's defenses, candidate Colt Grice suggests that Magath send out the Jaw and Cart Titan. Magath refuses, pointing out the Allies' anti-Titan artillery and the great risk of losing their Titans against it. Magath intends to send his Eldian unit to attack the train, but Warrior candidate Gabi Braun offers to use a bundle of grenades to destroy the armored train carrying the artillery on her own. Magath refuses to waste the candidate needlessly, but eventually gives in to Gabi's pestering. Once Gabi succeeds in destroying the armored train, Magath sends out Porco Galliard to attack the fort.
As Galliard and Pieck lead a charge against Fort Slava's defenses, Magath remains behind with the Warrior candidates. When the time comes for Zeke to make use of his Beast Titan to rain Pure Titans down upon the fort, Commander Magath and the Warriors watch from a distance as Marley's Titans complete the assault on the fort.
Some time afterward, the leaders of the Marleyan military convene to review the world's reaction to the end of the war between Marley and the Mid-East Allied Forces. Magath explains to the outraged general of the military that the technological progress of the world is overcoming the Power of the Titans. Magath states that Marley has been too reliant on the power of the Titans, allowing other nations to surpass them in technological might. Magath proposes that with the progress being made with aerial weaponry, Titans may become useless in future wars. Zeke proposes that Marley must acquire the Founding Titan to gain full mastery over the Titans as soon as possible while focusing on developing conventional weaponry, an idea which impresses the general.
After the meeting, Magath meets with Zeke and Colt, to discuss the likelihood of Zeke's plan working. Noting that 32 Marleyan ships have gone missing while attempting to scout out Paradis Island, Zeke and Magath conclude that there are likely two Titans, including Eren Jaeger, defending the island, and that they will need battleships when they attempt another invasion.
Magath later departs on a train towards Liberio. Despite the Eldians at the back of the train making a loud ruckus, Magath allows them to continue with the celebrations, noting it is only for a single night. When the train reaches the Warriors' hometown, Magath gets off the train with the others and escorts the Eldians into the internment zone.
Whilst the Eldian Warriors hold a private, unofficial meeting, Magath is a part of a team tapping the meeting to test the loyalty of the Warriors. He is slightly disappointed by Zeke's comment that insinuated that the meeting was being tapped.
Magath is paid a visit by the Tybur family and is greeted by the family's current head, Willy Tybur. Speaking privately, Willy asks Magath if he is able to tell which Tybur is currently in possession of the War Hammer Titan, but Magath insists he cannot. Magath notes that his leader at headquarters left earlier that day after receiving orders from his superior, and because of that, Magath is now speaking to Willy in this place. He asks if the timing is truly unrelated. Willy declines to answer, claiming that he came to see the statue of Helos, the Marleyan hero who slew the Devil of All Earth. He praises the figure as the spirit of Marley and Magath agrees, remarking that the statue is hollow. Magath intends to reinstate conscription for Marleyans, so war is something more to them than something they read in the newspaper, though he doubts it will be enough to stop Marley's self-destructive march to war. Under the assumption that he is speaking to the true power behind Marley, Magath tells Willy that it is too late.
Noting Magath's insinuation, Willy reveals that the Tybur family is, as Magath suspects, the true ruler of Marley. However, he insists that Marley's penchant for war has always existed, and that the Tyburs merely allowed the nation to do as they wished as penance for their suffering under Eldian rule. With the passing of time and the obsolescence of the power of the Titans, Willy is concerned about Paradis Island. Commenting that Marley needs another Helos, Willy entreats Magath to work with him. Shortly afterwards, Magath is chosen to become the next general of the Marleyan military when the time comes.
One month later, Magath is present at a meeting where the Warriors discuss potential Paradis Island invasion strategies with their Marleyan superiors, though the meeting does not end well. Later that day, he meets with Willy Tybur and hands him a notebook explaining the state of his "house," which Willy notes is in need of "demolition." Willy congratulates Magath on his inevitable upcoming promotion, and the two discuss the military and their country. Magath notices Willy's trembling hands as the latter expresses the burden that comes with his position of power. Changing the subject, Magath informs Willy that some "posts" in his house were still usable, and he has come to learn that "mice" have invaded his home.
As Magath and Willy head to the festival, they discuss the security involved in order to protect Willy and the officials present. Magath does not think it will be possible to defend everyone given that Willy wishes to be on stage and to bait their enemies with as many military officers as possible. Though Willy says Magath can limit it to the useless ones, leaving him free to rebuild the military with whoever he likes, Magath is concerned about the number of people who will die. This is not the war he is used to. They do not know their enemies, how they will attack, and there will be massive crowds of people.
He tells Willy that if he goes ahead with this, he will die, and he is too important to lose. However, Willy confides that if he escapes and is not among those sacrificed, the world will not listen to what he has to say. Magath agrees to go along with the plan, admitting that Eldians are devils, but so are he and Willy.
On the night of Willy's production, Magath brings an armed team atop a nearby building to observe the crowd for any suspicious actions. He takes a report and realizes that the soldiers who have gone to retrieve the Warriors have disappeared and the Warriors are missing as well. Magath has the reserves mobilized to search for them and notes that the event has begun. When the Attack Titan suddenly bursts out of the stage and murders Willy Tybur, Magath watches in shock as it begins a mass slaughter of the Marleyan military's top brass.
The War Hammer Titan emerges to combat the Attack Titan, but is quickly overpowered while Magath's subordinates rush to his side and remind him of their dire situation. Paying little heed to their reports, Magath fires his rifle at the Attack Titan to commence Marley's counterattack against the invader. Noting that their task to defeat the Paradis Island Eldians has been made much easier, he orders his men to head to their battle stations. The War Hammer soon regains the advantage and impales the Attack Titan on a massive pike of hardened flesh, though Magath reminds his soldiers that he dealt the first blow to their enemy.
During the battle between the two Titans, Magath's troops fire a barrage of anti-Titan artillery at the Attack Titan. Koslow wishes to kill the Attack Titan, but Magath insists that they support the War Hammer Titan so that it can inherit the Founding Titan itself, rather than kill Eren Jaeger and postpone the problem caused by the threat of the Rumbling. The War Hammer Titan quickly overpowers the Attack Titan and forces Eren to reveal himself, but before Eren can be captured Magath's forces are ambushed by soldiers from Paradis Island.
Magath and his troops escape the firefight into the shelter of a civilian building where Magath alerts all the nearby army and navy forces, ordering for the Liberio internment zone to be closed off. Magath notes to himself that just as Willy had planned, all the world would soon join the war against Eldia, though he wonders why the Paradis Island troops are proceeding with their plans knowing of this as well. His thoughts are interrupted when a bomb is sent into their room, forcing them to relocate.