When Enyo finally drags Theo out to a bar, at some point, she unlouds all this information on him.
The Tarotverse consists of 21 Worlds, which the elves say matches with the identities of the 21 surviving Celestials, godlike beings that formed the Tarotverse and put themselves into the Tarotverse at its creation.
Elven myth describes meetings with the celestials ten thousand years ago when the elves first discovered the keys--a magic sword, a wand, a cup, a coin, and a cloak. They call these five objects the TAROT, the Elven word for key and also an acronym for these five objects in this order when written in Elven. Using these keys, the elves eventually traveled to the 21 worlds described to them by the Celestials. In most of these worlds, they hid their identities and only observed the bizarre similarities and differences between these worlds. They also learned the order of the worlds, and that they were World 3.
It was relatively recently, from the perspective of the ten thousand-year-old elven TAROT, that the other TAROTs appeared.
Within less than 1000 years, 20 other TAROTs appeared, about one every 50 years, and then nothing for 200 years. You are the first new group to even look like a new TAROT in a couple centuries.
The different TAROT groups from the different worlds have their own acronyms, but each is dedicated to prevent misuse of the gating technologies and transdimensional interference.
Some worlds have more magic and some worlds have less. The elves discovered that worlds with magic move at a slower chronological pace. The elves would travel from their world to a world without magic, realize they had forgotten something at home, pop back for it, and, upon returning, find hours had passed in the other world. Humans from dimensions without elves end up with ridiculous notions about the length of the elven lifespan.
The elves also learned how to travel into their world's past by travelling to another dimension and then back to their world, but aiming at a chronologically earlier point. TAROT established strict rules against time travel unless necessary to stop temporal interference.
Worlds One through 3 are much younger worlds than many of the others in the Tarotverse.
World One (Tarokh) is a world of magic, the most magical world of the Tarotverse. It is a world entirely unlike your own with none of the place names you are familiar with. According to the elves, this world is aligned with the Celestial known as the Magician. While not its largest city, the magical city of Tarokh lends its name to the world for TAROT visitors. TAROT calls both the city and the world 'Tarokh.'
World 2, technologically, has not reached the industrial era, but has a great deal of scrying magic. The elves that rules over World 2 defend the use of scrying magic as necessary to maintain order. This world is aligned with the Priestess. Both humans and orcs are a permanent underclass on these worlds, with orcs having it worst of all.
World 3 (the Seedbank) is the homeworld of the elves. Nicknamed 'The Seedbank' the elves have rescued rare or extinct species from the other worlds they have visited over the last 10,000 years. If it lived once on one of the 21 worlds, it lives still in the Seedbank. The elves of World 3 first met humans when they travelled to World 1 and found elves and humans sharing cities and encountered half-elves. They have rescued so many humans, however, that World 3 now has more humans than elves. This world is aligned with the Empress. Enyo suspects that your world's 'Seedbank' where Flora and Fauna took you contains some kind of hidden gate, thin spot, or transdimensionally capable entity to World 3. That's just the way these things work.
World IV (Eternal Rome) has very little magic, but is technologically (and chronologically) more advanced. After 3,000 years of Roman rule, Earth rules over a vast interstellar empire. This world is aligned with the celestial known as the Emperor. Aspects of the Elven religion have been adopted on this world; the Emperor is said to be the embodiment of the Celestial Emperor, and therefore a God. The other Celestials are slowly displacing older Roman deities.
World V (The Great Library) was the second world to form a TAROT team, but their TAROT formed not to explore transdimensional travel, but to stop it. Transdimensional travel by 'fictionauts' to the various pocket dimensions started in medieval times and became increasingly common. The World V TAROT fruitlessly attempts to stop fictionauts from messing with these shared subdimensions. The Great Library of World V contains all the tales that have been written in the Tarotverse, canonical and non-canonical, and is the best place to go when you need to plagiarize something for a creative writing assignment. Many fictionauts jump into a pocket dimension, mess around, avoid getting arrested, and head to the Great Library to find their adventure has already written itself. This world is aligned with the Hierophant. A religious group called the Canonites want to stop the Fictionauts from all their messing around with stories. The Canonites are particularly troubled when people of a different intersectional positionality (race, gender, etc.) take over the role of hero in these stories adding diversity.
World 6 (Eden) is all unicorns and naked people and constantly fruiting trees. The world drips with magic, but has few magic users. Magically enhanced gardens that cover the planet provide abundant food and shelter to the mostly tribes of humans that live there. The humans on this world are particularly beautiful. Elves and sentient visitors from other worlds often are drawn to the magical energy of World 6. Some don't leave. Don't visit; you'll just get your heart broken or never want to leave. This world is aligned with The Lover.
World 7 (Greece Triumphant) is a world in which the age of myth never truly ended. The Egyptian, Greek, and Norse godlings filled the world with their progeny. Technologically, it is far less advanced than your world. There are various nations and city-states, but all of them acknowledge the Greeks rule (according to Enyo).
This world is aligned with the Celestial known as the Charioteer. The Charioteer, Enyo says, is also known as the Valkyrie (by the Asgardians), because the 10,000-year-old Elven records about the first meeting between the Celestials and the elves of World 3 uses a word that could either mean 'wings of steel' or'wheels of steel', so they're not sure how the Charioteer is described.
World X (Roulette) is ruled by wealthy Rakshasa while humans are slaves, or meat, or gladiators. The culture is cruel, centered on gaming, and many humans will bet their souls; the Rakshasa, equally cruel, often take those bets. The Rakshasa led TAROT from World X believes that the Tarotverse was created by a great animal-headed god for its own sick amusement. These worlds are a game; the TAROT enforce the rules.
World 12 is a world in which greed and selfishness led a handful of narcissists to attempt to reshape the world and fail. They enacted this takeover by infiltrating a government project intended to PREVENT time travellers from messing with the timestream. That agency was called FATE (Final Authority over Temporal Entanglements). This corrupted FATE devoted itself to advancing their own timeline, trying to establish themselves and their 'Corporation' as an absolute power throughout history. They ended up in a post-apocalyptic nightmare they no longer had control over. This world is aligned with the celestial known as the Hanged Man. FATE agents, some from timelines that have been destroyed, hop through time fighting each other, trying to regain control of a world that is far too convoluted for TAROT to easily fix.
World XV (Hellworld) is a world from which the gates to hell have been opened. It's quite similar to your world, and, technologically, not far behind, but it has always had occult magic, so it is chronologically behind your world. In 1970, some cultists weakened the seals and the horsemen were unleashed. The gates to hell were literally blown open. With that influx of magic, time slowed to a crawl here. It's been the 1970s for 200 years, according to something Enyo calls Green Witch Means Time, which she says is centered on Eternal Rome's chronology.This world is aligned with the Celestial known as the Fallen One.
World 18 (Witchworld) has a history similar to yours and is technologically not far behind. Magic was largely unknown on World 18 until the 1600s when witchcraft became much more common. Witches were persecuted but not destroyed. The witches, in fact, became increasingly powerful. After a century of persecution, the 13 Covens made a deal with the non-magical power brokers in the United States; the witches would erase themselves from history as long as they were allowed to guide World 18 towards agreed upon ends. The Celestial aligned with this world is known by many names, but all of them mean the moon. TAROT exists in this world and serves as a liaison between 13 Covens to FBI. The year is 2020 in World 18.
World 21 (Whichworld) a world largely without magic, except when invaded from outside. At these points in history, a set of artifacts are found and a group of heroes appear to take up the mantle of TAROT until the artifact is banished and the magic disappears again. It's the most non-descript of worlds. The Elves assigned Whichworld the Celestial known as the 'World-spirit'. The year is 2020 in World 21.
The TAROTs from these different worlds have different names. In Elven, TAROT is the word for key and a word formed from the first letters in the elven words for "Cloak. Coin. Cup. Sword. Wand." World 7 TAROT stands for "Totally Awesome Radically Overpowered Team." On Witchworld (18) it stands for 'Tactical Arcane Response to Occult Threats'.