Eldraine

Eldraine is a plane from Magic: The Gathering, originating from the set "Throne of Eldraine". Coined as a mixture between Arthurian myth and fairy tales, the plane is chock full of knights, fairies, ogres, and all of the other trappings of European folklore. If you can think of a fairy tale trope, there is a very good chance that there's a card with some version of that trope from Eldraine.

The plane itself is generally split between two parts: The Realm and the Wilds. The Realm consists of 5 different courts, representing the 5 colors of Mana and human civilization. It was made after humanity overthrew the elvish lords that had long since enslaved them, and then took their empire for their own. As you would expect, the Realm is home to the Arthurian side of the plane, and houses most of the knights in the set. The Wilds are the places that the Realm has not taken over, and where the elves took refuge after they got their asses handed to them by the humans. Home to the fairy tale part of the plane, as well as most of the other non-humans. Eldraine is the birthplace of planeswalking duo Will and Rowan Kenrith. Garruk Wildspeaker also makes an appearance, where he finally manages to get rid of the black taint that Liliana Vess put on him, opening him up for further appearances down the line!

The Courts

The Realm consists of 5 courts, each representing the different colors of Mana, a specific virtue, and houses a legendary artifact unique to them.

• Ardenvale, the White-aligned court, and houses a majority of the knights on the plane. They represent the virtue of Loyalty, have a ton of cards with vigilance, and houses the Circle of Loyalty, a ring of brilliant white flame that every knight has to walk through as part of their initiation. If they are found worthy of being a knight, then they pass through the flame unharmed. If they don't, then they are burnt to a crisp. Mechanically, the Circle is a Knight payoff that becomes cheaper if you own a lot of knights, pumps your entire board, and makes even more Knights.
• Vantress, the Blue-aligned court ruled by a Wizard with no sense of right or wrong. They represent Knowledge and house the sentient Magic Mirror as their legendary artifact. The Magic Mirror pays you off for casting a lot of instants and sorceries by becoming cheaper, maxing out your hand size and slowly filling it up with loads of cards.
• Locthwain, the Black-aligned court ruled by the only elf to have held onto their power after the human uprising. Their virtue is Persistence, and their queen is a perfect example of that. WoTC makes it very clear that she has had many, many lovers throughout her immortal lifespan. Many knights aim to be the next lover to the Queen, as her lovers are wed to the Queen the day they set out on their quest to find the Cauldron of Eternity. After a year passes with no word from the knight, the Queen declares them dead and throws a party. The Cauldron of Eternity is a reanimation payoff, which rewards you for filling up your graveyard with targets to be brought back to the battlefield. However, whatever is in your graveyard is all you get, as the Cauldron shuffles back any creature that dies back into the deck.
• Embereth, the Red-aligned court that is all about fighting and winning. Representing Courage, the court is home to an eternal knight tournament that has gone on for so long, no one remembers how or why it started. Their legendary artifact is the Irencrag, a massive molten boulder that aspirant knights thrust their swords into to prove that there is courage in their hearts. Forged from the Irencrag is the sword Embercleave, which is both a combat trick and a piece of equipment, all in one! It gets cheaper to cast the more attacking creatures you control, has flash, and gives one of your dudes trample, double strike, and +1/+1.
• Garenbrig, the Green-aligned court that represents Strength. They suplex bears and houses the only source of fast-travel on the plane in the Great Henge. Mechanically, the Great Henge pays you off for having big dudes, taps for mana, gives you life, and gives you card advantage for playing more creatures while ALSO pumping them up!

Mechanics

Adamant: Cards with adamant reward people for using 3 or more of a single color, usually by turning the admittedly lackluster cards into pretty sweet deals. EX: BEAR SUPLEX

Adventure: The first mechanic teased in the set and the most involved mechanic in the set. Creatures with Adventure have two halves to them: a Creature half and an Adventure half, which takes the form of an instant or sorcery. By paying the requisite mana, you can cast that creature as an Adventure, which casts the spell much like any other instant or sorcery. Once it resolves, the Adventure put into exile, where it can be re-cast as a Creature later on. You essentially get two cards in one! EX: Realm-Cloaked Giant

Food: Foods are artifacts that can be tapped and sacked for 2 generic mana to give you 3 life, and usually come in the form of tokens. While this seems pretty boring compared to Treasure and Clues, Throne of Eldraine puts a couple of spins on it, firstly by making certain creatures and non-token artifacts also count as food, and by making a variety of payoffs that run on food. EX: Gingerbrute, one of the more memed cards of the set based on art alone.

"Non-human" Tribal: Representing the divide between the human-centric Realm and the diverse Wilds, there are a ton of cards that specifically reward you for playing non-human creatures. EX: Grumgully, the Generous

"Second Card Drawn": Less of a mechanic and more of a theme, there are a number of cards in Red and Blue that reward you for drawing your second card in a turn. The most notable example of this is Irencrag Pyromancer, which has the delicious effect of turning all of your cantrips into LIGHTNING BOLTS.

Settings of Magic: The Gathering
Pre-revisionist:	First Magic Sets - First Urza Block - Arabian Nights Legends - Homelands - Ice Age - Mirage
Weatherlight Saga:	Portal Starter Sets - Second Urza Block Tempest Block - Masques Block - Invasion Block
Post-Weatherlight:	Otaria Block - Mirrodin - Kamigawa - Ravnica - Time Spiral
After the Mending:	Lorwyn - Alara - Zendikar - New Phyrexia Innistrad - Return to Ravnica - Theros - Tarkir - Eldraine - Ikoria
Two-Block Paradigm:	Kaladesh - Amonkhet - Ixalan
Post Two-Block Paradigm:	Eldraine - Ikoria - Kaldheim - Strixhaven
Never in a standard set:	Fiora (Where the Conspiracy sets take place) - Kylem (Battlebond)