Alter Ego (アルターエゴ, Arutā Ego?) is an Alter Ego-class Servant working as one of the three Alter Ego apostles of the Alien God in the Lostbelts of Fate/Grand Order: Cosmos in the Lostbelt. They are working in tangent with the seven Crypters attempting to supplant the Greater History of Man with the Lostbelts.
He is described as a voracious, carnivorous beast whose voice it's akin to a ghost of an evil king who devour gods, rips them apart and make their flesh his own. An ego guided by a greater existence, whose core brims with evil and malice.
Shimosa Province: The Stage of Rivers of Blood and Mountains of CorpsesEdit
At some point, he met an alternative version of Amakusa, and both agreed to execute a plan to exterminate humanity.
He appears in the story as the Caster-class Caster Limbo (キャスター・リンボ, Kyasutā Rinbo?), being one of the responsible for the events in Shimousa, using black arts to corrupt several people and turn them into beings that spread destruction across Shimousa. His silhouette is seen for the first time when the Seven Heroic Spirits Swordmasters appear to welcome the last member, him being the one who personally carved the Curse of Annihilation and transforming him into the remaining swordmaster. He is the one who reactivates certain puppet, which he dispatches to accompany the Chaldea faction to lure them into a trap.
At the climax of the story, on the arrival of the Onri Edo, he is seen as responsible for the strange phenomenon of the of sudden day/night shift, as the one who summons the monsters that appear at night. He decides to appear in the castle gardens, where he presents himself as Abe-no-Seimei before the group, to their disbelief. When Musashi attack him, he decides to reactivate a version of the Curse of Annihilation in Danzou, causing the puppet to attack Chaldea against her will, as well as to release the horde of monsters he had saved for that moment. Seeing that it didn't work, Limbo decides to use the Curse of Annihilation onto Musashi to transform her into a Heroic Spirits Swordmaster, but she is saved by the Chaldea Master. Surprised that his empowered sorcery was easily undone, he was injured by Musashi who took advantage of his confusion. An angry Caster decides to summon the Great Spirit of Limbo to defeat Chaldea, but without avail. He is caught off guard by Fuuma who slash him, presuntely killing him.
Later, its silhouette is seen on the upper floors on the castle. He survived and had hidden his presence to attack Musashi by surprise, but is stabbed by Empireo at the last moment, who states how disgusted he is with Limbo's existence in his sight before apparently dispose him for good.
At the end of these events, an surprisingly alive Limbo appears annoyed about the outcome of the entire setting. After calming himself, he claims that, even if he failed to invade Chaldea, he have finally succeeded in finding the Lost History (Missing Belt). He then mentions that the "Satan" he was following was just a false name, a ridiculous joke that he got onboard with a bit too far, before sincerely apologizing to ■■■■■■■■■.
SIN: Land of Unified KnowledgeEdit
Yuga Kshetra: The Black Final GodEdit
Atop of God Arjuna's Vimana orbiting around the Fantasy Tree Spiral, he appears as the responsible of the sudden shortening of Yuga cycle, tricking the Lostbelt King on reenacting the cycle on a weekly basis due to his own wish of seeing what lies beyond the termination of the Maha Yuga, the last Yuga that would end the universe and the trichiliocosm. 
For some reason, he refers to the Fantasy Tree as the Tree of the Empty Rhetoric. It is later revealed the body he used in the Lostbelt wasn't his true one but his Saint Graph engraved on a shikigami.
He is shown using a kind of sorcery called Curse of Annihilation, with which he can turn servants, humans or puppets into genocidal beings who cannot avoid bringing death and destruction to all human life in sight. Those under the effects of the curse become undead beings that cannot be shot down by convectional methods, even with attacks from servants. Only a weapon that can cut through karma has be shown to be effective against them. 
He has the ability to change day and night at will, as well as to summon a Crimson Moon, which can randomly transform humans into monsters. He claims that both the Curse of Annihilation and this ability were granted by the mysterious being whom he jokingly calls "Satan."
He can make clones of himself engraving his Saint Graph in shikigamis, control them at will and disperse them whenever he pleases.
Creation and ConceptionEdit
Shouichi Furumi is the character designer for Ashiya Douman.
- ↑ 1.0 1.1 Fate/Grand Order: Epic of Remnant - Shimosa Province: The Stage of Rivers of Blood and Mountains of Corpses, Chapter 16
- ↑ 2.0 2.1 Fate/Grand Order: Epic of Remnant - Shimosa Province: The Stage of Rivers of Blood and Mountains of Corpses, Chapter 2
- ↑ 3.0 3.1 Fate/Grand Order: Epic of Remnant - Shimosa Province: The Stage of Rivers of Blood and Mountains of Corpses, Chapter 14
- ↑ Fate/Grand Order: Epic of Remnant - Shimosa Province: The Stage of Rivers of Blood and Mountains of Corpses, Chapter 15
- ↑ Fate/Grand Order: Cosmos in the Lostbelt - SIN: Land of Unified Knowledge - Prologue
- ↑ Fate/Grand Order: Cosmos in the Lostbelt - Yuga Kshetra: The Black Final God
- ↑ 7.0 7.1 Fate/Grand Order: Cosmos in the Lostbelt - Yuga Kshetra: The Black Final God, Chapter 19
- ↑ Fate/Grand Order: Epic of Remnant - Shimosa Province: The Stage of Rivers of Blood and Mountains of Corpses, Chapter 3