Avenger's True Name is Amakusa Shirou Tokisada (天草 四郎 時貞, Amakusa Shirō Tokisada?), the teenage leader of the Shimabara Rebellion. This version of Amakusa is a traveler from a culled parallel world, much like the female Miyamoto Musashi.
Due to his experiences in numerous parallel worlds, he has despaired of the human condition and his personality greatly differs than his counterpart.
Shimosa Province: The Stage of Rivers of Blood and Mountains of CorpsesEdit
He is the known as the Sorcerer (妖術師, Yōjutsu-shi?). Having traveled several worlds, he eventually had a revelation from a unknown being, who gave him instructions on how he can carry out his revenge against the mankind. At some point, he meets Caster Limbo and together they decided to carry out a plan to exterminate humanity.
Due to a weak Counter Force on the timeline and several requeriments fuilfilled, he choosed Shimousa as the right place to execute his agenda without so much oposition. He and Limbo decided to summon several servants and engrave upon them the Curse of Annihilation, turning them into undead, bloodthirsty monsters, thus creating the Heroic Spirit Swordsmen, whose purpose was to massacre every human life on sight without exception, and using the negative energy of the souls of the victims as fuel to activate the Onri Edo upon the Castle of Toke.
His main goal was the completion of the Onri Edo with the sacrifice of a princess of the Matsudaira clan. According to him, once the ritual is complete, not only that timeline will be engulfed by the darkness, but, like a curse transcending worlds, it will affect every timeline where the Tokugawa clan has left a trace in history, eventually reaching Chaldea and bringing a great calamity to the Time Tree itself.
As an Avenger, Shirou Amakusa is an extremely powerful being, whose body has long since surpassed the limits of humanity becoming equal to that of a Heroic Spirit Swordmaster. Due to this, he is able to fight Muramasa and Kotarou at the same time without taking damage, albeit Muramasa was only wielding a "pathetic little knife". He also boasts the ability and sorcery to summon and corrupt Heroic Spirits stems from a being he calls "Satan."
In this form, Amakusa Shirou possesses the Shimabara Hell, a Reality Marble that reenacts the hell that he lived in the Shimabara Rebellion in which he was the sole survivor. The air inside the reality marble is highly poisonous and it would burn to ash the lungs of anyone should they take a single breath without being careful enough. Inside of it, Musashi feels useless due to not having anything to cut, and she no longer receives Lady Kannon's protection due to the marble being completely closed off.
It was ultimately destroyed by Muramasa's Tsumugari Muramasa. Shirou was shocked when this happened, and Muramasa explained it was because Onriedo Castle shares part of its name with Edo Castle. The name Muramasa is synonymous with the Tokugawa's downfall, so Amakusa Shirou would have succeeded if he didn't rhyme the name of his castle with the Tokugawa's own.
- ↑ 1.0 1.1 1.2 1.3 Fate/Grand Order: Epic of Remnant Shimosa: Section 15 Ultima Cantica: The Stage of Carnage, Onriedo (Ending)