Baobhan Sith (Fairy knight Tristan)

Calamity: During 12,000 BC, Britain was destroyed by Sefar due to the Fairies of the Beginning not forging Excalibur. Although a new island was built using the corpses of Cernunnos and other fairies, the will of the original Britain was still very disgusted with them. Due to this, it sent Calamities after them to try and wipe them all out, Cernunnos being the only exception. The Calamities appear every hundred years, and the Great Calamities every thousand.

Moss: When Fairies die, their corpses change and become part of Britain. However, Fairies in the Lostbelt who die by losing their purpose become Moss life that can no longer speak or hear, the black algae that pollutes the world with its existence, the curse of Britain, killer of Fairies. The Moss are a curse affecting most the Fairies in this Lostbelt, originating from the six A-Rei who founded Faerie Britain on their sins. All Faeries descended from the six who betrayed Cernunnos are doomed to waste away as punishment for their sins and refusal to repent.

Lostbelt: As opposed to the Proper Human History, the history of "winners" born from correct choices and proper prosperities leading to the "present", the history of "losers" born from the wrong choices and mistaken prosperity is cut off. Considered "unnecessary" and cut off from becoming even parallel worlds, this history which has hit a dead end is known as a Lostbelt. 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

British Lostbelt: The British Lostbelt esignated Order Lostbelt No. 6, Time flows differently inside the Lostbelt than outside. At the Wandering Sea, Chaldea is warned that they only have 24 hours before the Lostbelt self-destructs and takes the outside world with it. The Lostbelt has existed for 14,000 years. The Lostbelt's true divergence point from Proper History was the absence of Excalibur, leaving Earth with no way to properly defend itself from Sefar. Six fairies (who would later become the founders of the fairy clans) were tasked with forging the Holy Sword, but chose not to out of sheer laziness. This resulted in Sefar succeeding in the Velber's goals by wiping out all life and landmasses of the planet with the exception of Avalon, which the fairies could never return to as "only those free of sin may pass", leaving them to buffeted by the endless ocean's giant waves. Eventually, Gaia sent Cernunnos from the Inner Sea of the Planet to properly punish their failure, but it felt the fairies had already suffered enough. Instead, it allowed them to live upon its body alongside the last surviving human, who Cernunnos had taken as a wife and priestess.

The fairies were ungrateful, however, and pestered Cernunnos to create a new home for them, something it could not do. The Priestess chastised them to reflect on their actions. Instead, the Fairies concluded that Cernunnos’ titanic body would make a nice landmass to live on. They held a celebratory feast and lied to Cernunnos about wanting to become its worshipers and offered it drink. Cernunnos, believing the fairies had finally repented, gladly accepted the offering despite its priestess's disbelief and suspicion. She was correct; Cernunnos was killed by the poison in the drink, and the fairies fashioned its corpse into a new Britain.

While previous Lostbelts could still be called "human history", the world of the English Lostbelt is a "fairy history" where fairies have dominated for thousands of years. Furthermore, the only landmass in the entire world is the island of Great Britain, while the rest of the planet is just an ocean. The concept of other countries does not exist.

The reason for the EX-Rank Lost Depth is not only due to Sefar wiping out all life on Earth, but because there was no life at all when the Lostbelt was intially founded. Indeed, when Beryl first arrived, the Lostbelt was a barren and lifeless land, as the Fae had long since betrayed each other and driven themselves to extinction due to their innocently capricious and merciless nature; to fufill their personal enjoyment and purpose, and get rid of anything in the way.

There is no human civilization in this world, no concept of families, parents and children. The 'modern' humans who exist are livestock used to perpetuate Fairy pleasure and are not 'born'. They are created by a method of cloning the body parts of the last remaining human; Cernunnos's priestress who had been torn apart and kept alive for 14,000 years by the founders of the Fairy Clans. The Fae instead mimic human civilization from Proper Human History

Humans in the Lostbelt are incapable of breeding and terms like "parent" and "child" do not exist, instead terms like "previous generation" and "current generation" are used.

Singularities are unobservable regions that do not exist within Chaldea's recorded history. It's as if a hole has opened up within the timeline, a hole that is separate from the regular temporal axis. If Human History is thought of as one long scroll, Singularities are like stains that weaken the scroll by contaminating the history around them.

Under ordinary circumstances, a Master is always a spellcaster, usually a Magus with a Magic Circuit, who is selected by the Holy Grail. It is possible for an ordinary person to become a Master, An active Master will also possess a Command Spell somewhere on their bodies as a visible proof of their contract, the role of a master is to command their servants and supply magical energy to them

Servants are Spirits made into special Familiars of the highest rank, referred to as Ghost Liners by the Mage's Association, that are bound to the Master. Typically Heroic Spirits under most systems, they can also sometimes be Divine Spirits, Phantoms, Wraiths, and living people depending on various circumstances.

Chaldea is a secret agency founded with the purpose of preventing the "certain extinction" of the human race. It specializes in handling temporal anomalies and other existential threats to humanity. The hidden purpose of the organization is the enaction of the Human Order Revision Incident by CHALDEAS in following Marisbury Animusphere's Grand Order.