Lostbelt

Cosmology of TYPE-MOON
Key Terminology
Nasuverse
Root
Universe
Alternate History
Planet
World
Time Terminology
Time
Alternate History
Quantum Time-Lock
Parallel World
Singularity
Lostbelt
Lost World
Timeline
Space Terminology
Dimension
Universe
Celestial Body
Archetype
Counter Force
Ultimate One
Earth
v

A Lostbelt (異聞帯(ロストベルト), Ibuntai(Rosutoberuto)^?, lit. "Belt of Strange Tales") is a Pruned Event recreated by a Fantasy Tree.

Characteristics

A Lostbelt is a history which has hit a dead end, considered "unnecessary" and cut off from becoming even parallel worlds. If one thinks of Human History as one long scroll, the Lostbelts are like another scroll entirely that was discarded once it was clear it was no longer useful. As opposed to the Proper Human History, the history of "winners" born from correct choices and proper prosperities leading to the "present", a Lostbelt is the history of "losers" born from the wrong choices and mistaken prosperity.

It is unknown how exactly that the timelines selected by the Fantasy Trees managed to exist until the present day, as they would have ceased to have exist entirely within a century of being designated for culling due to Quantum Time-Locks. Despite this, these Lostbelts are being wielded as weapons against the world of Proper History itself in an incident known as the Filtering Outsider Phenomenon (濾過異分子現象, Roka Ibunshi Genshō^?, localized as "Felling Theoretical Phenomenon"). Ophelia Phamrsolone proposes the theory that the specific timelines that we see within the Alien God's Lostbelts are actually virtually simulated from their point of culling unto present day using the resources within the Tree; and then iterated without, unto the Tree's environs, the surrounding environment. This is abstractly akin to Emiya Shirou's Projections — rendering into the real world the product of a simulated history, then imposing that simulated history over the Proper Human History in the hopes of replacing it with the Lostbelt's version of history.

The Fantasy Tree then selects a Lostbelt King, a powerful figure who is given the ability to direct the Tree's growth and spread, making the Lostbelt more stable and expanding its scope. The Fantasy Tree also begins gathering energy, which is used to prepare for the descent of the Alien God. The Alien God's true intentions for the Lostbelts as well as the Human Order Revision itself are currently unknown. Destroying the Fantasy Tree sustaining the Lostbelt will allow the culling process to resume, and a Holy Grail formed from the Fantasy Tree's remains can be collected. A Lostbelt without its Fantasy Tree can last no more than a few months (from its inhabitants' perspective- an outside observer will see it vanishing immediately) before the culling process is completed, at which point the Lostbelt and all of its surviving inhabitants will be erased from reality as if they never existed. It is unclear if erasing all the Lostbelts is enough on its own to undo the bleaching of the world, but it is likely to be a necessary step towards doing so.

The events of the Edo Singularity reveals a unique "Subcategory Singularity" (亜種特異点, Ashu Tokuiten ^?, localized as "Pseudo-Singularity"), designated the Humanity Destruction Zone, that is able to effect Human History akin to a Lostbelt but while trying to remain a Singularity, when normally Singularities only affect what's within the Singularity's borders. She compares the one in Edo to others such as the Shinjuku Singularity and the Shimosa Singularity as places isolated from standard history.

The Shimosa Singularity is considered Subcategory Parallel World (亜種並行世界, Ashu Heikō Sekai^?, localized as "Pseudo Parallel World"), also known as a Micro-Lostbelt (小さな異聞帯, Chiisa-na Ibuntai^?), as it is something close to a Parallel World but not quite one. A Lostbelt that was both a part of human history but also not part of it. It is a world observed by the God of a Distant Star and a world resembling a Singularity yet isn’t one. An otherworld (異界, ikai^?) rift which exists between dreams and reality, distinct enough that it should be designated for culling but hasn't been. A closed-off subspace not unlike a Reality Marble, a separate timeline, or an alternate world. Due to its isolated nature, the Counter Force is apparently somewhat weaker there, though as it is not within the standard history (but at the same time, not within another universe), the events within should not be able to threatened history. Despite this, with the summoning of Onriedo Castle by Amakusa Shirou's Reality Marble, the events of the world would switch from dream to reality and become quite real. If Amakusa's reality marble was able to fully take root in that world and activate its curse, not only would it destroy that world, but threaten to destroy many other worlds too, including the world of Chaldea.

The Heian-kyō Lostbelt was capable of becoming a Subspecies Lostbelt (亜種の異聞帯, Ashu no Ibuntai^?), using a ritual to grow and mature a Fantasy Tree but using the Onriedo Castle summoned in the Shimosa Singularity, a castle from a pruned Lostbelt, as equivalent for a Psuedo-Fantasy Tree; a Subspecies Fantasy Tree (亜種空想樹, Ashu Kūsōju^?). This is something that is both a Singularity and a Lostbelt due to being a Lostbelt occurring in 1008 AD, Heian period Kyoto from Proper History. Due to this, the city will become a different world, while at the same time be taking root in Proper History and destroying the future.

Meanwhile, the British Lostbelt reveals that the magical energy of a Lostbelt's Fantasy Tree can be used to turn the Lostbelt into a Singularity - a Fantasy into a Reality - through Rayshifting within the Lostbelt itself, with Morgan Le Fay on Proper Human History and the future of the Lostbelt to the version of her within the Lostbelt's past. Turning a Lostbelt into a Singularity requires the Fantasy Tree to wither and die, as as long as the Tree remains, nothing can be changed in a Lostbelt; any element added causes history to adjust in real-time, even if it isn't consistent. Only when the tree disappears can there be an opportunity for a fantasy to become reality if one can sustain the "world" afterwards, which she could sustain through the vast magical energy in her Summoner's Throne from her "existence tax" on the lifeforce of her fairies. If the original distortion of history, the origin point and foundation of the Lostbelt, is corrected - in this case, the original "Holy Sword" not being forged - then the Singularity will be resolved and eventually the Lostbelt's contents will never have existed without its Fantasy Tree to sustain it. Consequently, should this Singularity merge with Proper Human History, then its history would become part of Proper History - in this case, Proper History will lack the Concept of the "Holy Sword", Excalibur.

Turning a Lostbelt into a Singularity changes the history of a Lostbelt and make it "real", a new history capable of comparing to Proper Human History with its "strength", becoming a "Lost World". Because they are as real as inhabitants from Proper History, some Lostbelt inhabitants are able to exit a Lostbelt and can emigrate to Proper History without disappearing. However, in the British Lostbelt's case, as the humans of the Lostbelt are not natural lifeforms and with no reproductive ability, and were created back when the Tree was still alive and history still a fantasy, they remain a fantasy that can only exist in the Lost World. Meanwhile, the fairies are real and can exist in Proper History, as they could be born after the Lostbelt became real. As the time before the Tree died is still considered a "fantasy", it allows for an amount of discrepancy, such as sending a Calamity or a person from Proper History back in time, as no matter how much the Fantasy history changes as a result, the beginning of the "real" history when the Tree dies is set in stone. Once the Tree withers, those time-travelled elements disappear as it contradicts the event of the real history, and inhabitants with memories of those contradictions will revert to the previous version of events without the time-displaced elements. However, if those elements do not make any contradictions in history until they reach the time when they were first sent back in time, they can avoid the paradox and prevent disappearing. Despite this, after history becomes "real", if someone from the Singularity recognises an individual from the Lostbelt as something different to what "real" history says, or an individual from the Lostbelt remembers someone from the Singularity, then the individual from the Lostbelt will become someone who "should not exist" and be erased due to the paradox; memories of that individual will, however, remain.

Following the attack on Chaldea in 2017, the bleaching of the world and the declaration of rebellion against the Proper Human History, with the threat of a regression into the Age of Gods and the recreation of the world, the survivors are forced to use an experimental method of navigating through Imaginary Number Space, through the Lostbelts, in order to resolve the incident.

After all of the Lostbelts have been established, the Crypters seek to expand the "domain" of their own Lostbelts, which will eventually clash with the other Lostbelts. The one that is built by greater Human Foundation will end up overtaking the weaker one and use it as "nutrients". This process will allegedly continue, until only one Lostbelt is remaining.

Koyanskaya describes the Proper Human History as "easy mode" and the Lostbelts as "hard mode", though the veracity of her statement has yet to be fully determined.

Lost Depth

Similar to the Human Order Foundation Values associated with the Singularities, the Lostbelts have an associated value known as a Lost Depth (異聞深度, Ibun shindo^?, localized as "Lostbelt Depth").

Lost Depth follows Parameter Rules. Devised by Sion Eltnam Sokaris, Lost Depth is a measurement of how "strongly [a Lostbelt] refutes Proper Human History". It takes into account the factors of how much each Lostbelt differs from Proper Human History. The relative age of divergence between each Lostbelt doesn't inherently affect the ranking, but rather how the humanity of the Lostbelt has come to live. The inhuman Yaga of the Russian Lostbelt lost their humanity, but they retained a cultural system closer to Proper Human History than the farmed humanity of the Scandinavian Lostbelt.

Another value assigned to each Lostbelt is its Proper Human History Resemblance (汎人類史残存数値, Han-jinruishi zanson sūchi^?).

Known values

Lostbelt	Lost Depth	Proper Human History Resemblance	Notes
Russian Lostbelt	D	Unlisted
Scandinavian Lostbelt	B+	Unlisted
Chinese Lostbelt	E	E
Indian Lostbelt	A	C
Atlantic Lostbelt	A+	Unlisted
British Lostbelt	EX	Unlisted
South American Lostbelt	A++	Unlisted