Tir Nan Og

Tir Nan Og was a fairy kingdom of Earth and the highest fairy kingdom on Earth before the Liberation Conquest of Earth which destroyed many fairy kingdoms on Earth. All fairy kingdoms on Earth recognize Tir Nan Og as the highest ruling body of Earth for the fairy order.

Early History
Tir Nan Og were the fairy base on Earth. Fairy hunters also came in to try to stop the fairies. Fairies killing other races caused humans to be one of the only intelligent native species on Earth. Fairies acted hiddenly on Earth using pocket realm magic and settling in sparsely populated areas to set up their kingdoms, enchanting the area surrounding to put their magic. Fairy kingdoms became set up on Earth but they recognized Tir Nan Og as the highest rulers of Earth for the fairies. They kept the last intelligent race under their control for a long time that is until the Wizards of the Black Circle came in.

The Wizards of the Black Circle
The Wizards of the Black Circle triggered an event that would change the course of Earth forever. The event to the fairies were known as the Great Fairy Hunt while the fairy hunters called it the Liberation Conquest of Earth. What they did is that they destroyed many fairy kingdoms and hunted down multiple fairies on Earth leading humans to be liberated from fairy control. Taking down the largest fairy kingdom Tir Nan Og and ending it.

Afterwards
After the end of Tir Nan Og, fairy kingdoms still continued on Earth but started losing grip of the world and eventually being fully ended after the two world wars.

Society
Tir Nan Og society reflected Earth of the medieval ages and assimilated into Celtic culture. Major figures like the Major fairies are considered the balancers of nature and the symbol of order, In Tir Nan Og alone, many fairies took feudal ideas of feudalism and used it in their daily lives. Fairy circles were used a lot as ways to communicate with each other. Besides that technology wise isn't that advanced and most used weapons similar to the ones used in the medieval ages. Every fairy kingdom reports to Tir Nan Og and considers them as their king and queen. Holidays include:

Monarch Birthday
Celebrates the birthday of the current monarchs.

Environment and Geography
It's very fresh and lusciously, this is because of the nature magic in Tir Nan Og. There's a mountain in the middle of the island with magical plants and creatures everywhere though they all resemble a creature on Earth and not some alien creature.