Gigantomachia/Synopsis

History
Gigantomachia was a member of the League of Villains before even Tomura Shigaraki was. He once served as All For One's bodyguard, during his reign of terror, although it is unknown for how long.

Foreseeing his inevitable downfall, All For One decided to hide Gigantomachia in the mountains, with implications that All For One groomed it into a safeguard in the case that the situation of the League comes to a point that they are at risk. Then he advised Kurogiri to use him once he believes to no longer be capable of ensuring Tomura's safety.

Months before the start of the tests to access the U.A. High School, Gigantomachia was walking through the city towards the Springer's Hero Office, but he got lost. He threateningly asked two middle-school girls for its location, but the girls were too terrified to utter anything. Gigantomachia took their silence as offensive and put his hand on a building, which caused the building to start breaking down.

Suddenly, Mina Ashido jumped in and made up some directions. Gigantomachia thanked Mina as he wandered off while rambling about everything he does is for his master.

Vs. Hero Killer Arc
Alone in the woods, Gigantomachia listens to a radio report about Stain's defeat.

Shie Hassaikai Arc
After All For One’s defeat, Kurogiri informs Tomura about the "power" All For One left behind and wondering if he should retrieve it to advance the League of Villains.

Kurogiri began searching for Gigantomachia in the mountains. However, Gran Torino and Naomasa Tsukauchi have managed to track down and find Kurogiri with the help of eyewitness reports and have subdued him. Kurogiri asks Gran Torino if he knows of the rumors about a "ruffian" appearing on the mountain where they are at and the reason he is here is to speak to the "ruffian". Gran Torino would prefer Kurogiri to tell him all about it behind bars. Suddenly, a huge noise reverberates in the area which catches Gran Torino's attention, and Gigantomachia makes an appearance.

Gran Torino and Naomasa are seriously injured and the task force suffers severe casualties at the hands of Gigantomachia, but they manage to take Kurogiri into police custody, at the cost of allowing Gigantomachia to escape, after having completely destroyed a large portion of the mountain. Later, Gran Torino phones All Might to inform him that they captured Kurogiri, and also to warn him about the threat posed by Gigantomachia, which he defines as a walking disaster.

Meta Liberation Army Arc
Sometime between late September and early October, before the Hero Billboard Chart JP, Gigantomachia finally meets Tomura and the new League of Villains. Tomura expresses glee as he realizes that Gigantomachia must be the power Kurogiri mentioned to him. Dabi and Mr. Compress are stunned by his appearance.

After setting down his radio and confirming Tomura's identity, Gigantomachia challenges the League to see whether they are worthy of his loyalty. Gigantomachia easily prevails over the League managing to incapacitate Himiko Toga, Twice, and Mr. Compress.

He is dismayed at their performance, tearfully crying out that Tomura is too weak to be a successor, calling the League unacceptable while questioning All For One's motives. He comments that he wants to accept Tomura but can't. A tearful Gigantomachia proceeds to smash the ground, causing all League members to lose their footing. Gigantomachia's sheer power ends up destroying the majority of the landscape.

During the confrontation, Kyudai Garaki speaks to Tomura through the Gigantomachia's radio, regarding his uncertainty in the League's current state and the need for help. Kyudai explains that Gigantomachia has unlimited stamina and did not require any modifications to serve All For One as bodyguard and confidant. He reveals that All For One hid him to make sure his legacy would live on through Tomura's command.

Dabi questions his usefulness, with the Doctor proclaiming that Gigantomachia is loyal to a fault, so he’s in despair when faced with Tomura in comparison. Dabi shoots a wave of fire toward the giant brute, but he simply charges straight through it, completely unaffected by it.

Before Gigantomachia continues his attacks, a voice recording of All For One plays from the radio. It effectively calms Gigantomachia as he nuzzles and purrs at the radio. An irritated Tomura states that he does not want Gigantomachia. The Doctor responds with Gigantomachia can be useful and warps the League to a secret laboratory filled with multiple Nomus to continue the conversation.

After their conversation, Kyudai instructs Tomura to get Gigantomachia to submit. Kyudai has the League, minus Dabi warped back. A confident Tomura tells Gigantomachia that the 'future king has returned'. An amused Gigantomachia replies that a king should 'inspire dread, be admired, and be strong'.

The fight continues and goes on for weeks. While he fights the other members, he ignores them and mostly focused on fighting Tomura who still possessed a stronger resolve. Gigantomachia calls his efforts weak but isimpressed by his determination. Gigantomachia would fight and go to sleep while the cycle continues.

During one of their breaks, Re-Destro, supreme commander of the Meta Liberation Army, contacts the League and challenges them to confront their organization, under the menace of revealing their position to the heroes if they refuse. Tomura accepts the challenge and decides to take advantage of it to kill two birds with one stone: He plans to use Gigantomachia against the Meta Liberation Army. Gigantomachia will inevitably crush Re-Destro's army, but will be weakened enough so he can defeat him and subdue him to his will.

Ujiko warps the League to Deika City, where they face off against the Meta Liberation Army in an event known as the Revival Celebration. Throughout the battle, they are aware of the time until Gigantomachia awakens, however the MLP is stronger than expected and they take chances of being defeated before this happens.

Doctor Garaki, who has been listening in on the fight, notes that it would be sad for All For One for his protege die here, so he uses another record of All For One to prematurely awakens Gigantomachia and ordering him to the League's location. Gigantomachia erupts from the ground, and when he notices that the League was gone, he uses his nose, he tracks them down after catching Tomura's scent.

Gigantomachia arrives and runs through the city, while easily sweeping aside everything and everyone in his path. While closing in on Tomura's location, Gigantomachia is nearly impeded by Geten with the ice user's Quirk. However, he easily swats the latter away and continues on his path. Gigantomachia finally reaches Tomura's location but stops once he sees Tomura embracing his true evil.

After half of Deika City is turned into a barren wasteland by Tomura's awakened Quirk, Gigantomachia can only look in awe while he witnesses Tomura emerge victorious over Re-Destro who concedes defeat and control of his army to Tomura. As he looks at the sight, Gigantomachia mentally compares the proud Tomura to All For One and sheds a tear of joy at seeing Tomura truly being his master’s successor.

Sometime later, Gigantomachia is at the ceremony Re-Destro holds in honor of Tomura. While in the audience, he bears witness to the creation of the Paranormal Liberation Front that will be merged from the League and the Army.

Endeavor Agency Arc
After the organization's formation, Gigantomachia and his allies (excluding Tomura and Geten) are present at a meeting in which Hawks informs them of Endeavor's decision to take on two new interns other than Shoto.

Paranormal Liberation War Arc
When the raid commenced, Gigantomachia was sitting in the underground bunker, holding the radio in his hands, waiting for his master's orders. When Tokoyami unleashed his Dark Shadow's Ragnarök, Gigantomachia didn't react to it at all, but Dark Shadow still called him a "real monster". As the fight continued, he still blankly looked at the radio.

After Present Mic broke his vat, Tomura awoke due to the electronic shock. Gigantomachia them picked up his master's scent and stood up. Awoken, Tomura started decaying the area around him and after he finished, he picked up Kyudai's phone and ordered Gigantomachia to rally the Front's members and bring them to him, to which he replied roaring. He then increased in size and broke through the villa's floor, coming to the battlefield for the first time since the raid started.

He soon picks up some of the lieutenants and heads towards Tomura's location. However, he was stopped by Mt. Lady, who swore she wouldn't let the giant pass. He completely ignored her presence, until he chose to change directions to the shortest route to Jaku City, which he grabbed her leg and threw her away. Despite that, he was slowed down when Kamui Woods entangled her to Gigantomachia's leg using his Quirk.

Later, the U.A. students manage to pin him down and are trying to throw the sedative into his mouth, hoping to put him to sleep. He stands up, only to fall once again, as some explosives were put in the ground. Mt. Lady suddenly jumps on his back, opening his mouth, while Mina Ashido breaks through the wall of fire created by Dabi using her Acidman and prepares to throw the sedative into Gigantomachia's mouth. The heroes start swarming his back, engaging the lieutenants.

Gigantomachia proclaims there is no need to waste time on flies, as he decides to shake the heroes off so they can't regroup. He tosses Mount Lady away and knocks her out. He tries to grab Mina, though suddenly, Red Riot intervenes and saves her from being crushed by his giant left hand. The giant stands up, and grabs his master's comrades, saving them from falling to the forest floor.

All of a sudden, Red Riot climbs up the giants' arm, and throws Mina's sedative canister, only for it to stopped and shattered by Himiko's knife. He takes out another one, his own sedative canister, and proclaims that Mina's chivalry won't go to waste. As he throws it directly into his mouth. The giant tries to grab him, although Tokage catches him as the U.A. students open fire on Gigantomachia with cannons created by Momo's Quirk. Majestic, Fat Gum and the other pro-heroes move in on his location, as the giant's lower canine jaw begins to move on his eyes. Gigantomachia is irritated, proclaiming that the flies are never-ending.

Later, it's shown that Gigantomachia has defeated the heroes and is heading to Jaku City, destroying everything standing in his way. He hasn't beaten the U.A. Students, because they had been transported to safety by Majestic. The rest of the Paranormal Liberation Front's soldiers are following behind him as he lays waste to the cities.

In a few moments, he's already in Sairo City. As he's rampaging through the buildings as if nothing's there, he notices how there are two of his master's scents. The Heroes start mobilizing to confront Gigantomachia, who was heading straight for Nabato City at 100 km per hour while tearing through the buildings as if he was a mole digging through the dirt. As the battle against Tomura turns in the favor of heroes, Gigantomachia finally reaches his master's location. Shoto and Nejire Chan unleash their powerful Super Moves on Tomura, attempting to finish him off, but the giant interrupts them and saves Tomura from certain death.

He puts his master on his back, hoping that his comrades could awaken the unresponding Tomura. As Gigantomachia awaits for orders, suddenly wires from the sky wrap around the battlefield, as Best Jeanist descends from the sky. The hero restrains Gigantomachia and the League, while Spinner and Compress wonder how could Gigantomachia be pinned down so easily and Spinner realizes that Shigaraki must give an order for Machia to move. Tomura wakes up and orders the giant to fight back, prompting him to start breaking from the wires.

As the giant struggles, the wires start breaking and he manages to break free, only to have Endeavor fly up to his face and attack him as his last effort, as he knocks himself out by doing it. Gigantomachia falls on the ground and suddenly starts losing strength, as the students' anesthetic has started working. Unable to do anything, the behemoth lies on the ground, as more fibers start restraining his movements once again.

After the war concluded, Gigantomachia was successfully captured and detained by the heroes, with his transportation to Tartarus prison being planned. One guard questions why they couldn't just kill the behemoth and the other guard responds by saying that bullets would just bounce off him and using missiles to execute him would be considered unethical as he is still a human. The giant's planned transport however was cut short by the prison break caused by All For One (possessing Tomura's body) and a number of High End Nomus.

Following the Izuku's return to U.A. as well as the battle between "Tomura Shigaraki" and Star and Stripe, it is revealed in a conversation between Denki and Minoru that Gigantomachia is still sedated and confined in a facility built around him.