At the beginning of its story, Eriu was not divided; the partition of the world was decided after a 100 war originated by the death of the king Basileus, who ruled all over the species until Chaos, greater god of disorder, killed him.
Nowadays, every region is inhabited mostly by a specific species, as shown on the political map, but anyone can live everywhere they wish.
The Regions and the Climate
The weather is mostly mediterraneus, with a range variety of plantations, except for Lagin and Numu, where it's hotter (especially in the desert) but thanks to the oasis and the rivers people can still produce vegetables. In Ulaid too the weather is pretty different, because it's colder.
Ulaid, at north, it's the colder island, but the weather is still pretty good to have some agriculture. It's even one of the most isolated, and Icryses love it, because they prefer to live by their own.
Connacht, at west, is the region with the greatest number of forests and trees.
Mide, at the center, is the most fertile land, mostly characterized by plains and hills.
Lagin, at east, is mostly a desertic area: here strong winds blows and sometimes they cause some sandstorms, and they make this land the driest, but there are various oasis, and the big river that flows through almost all the area.
Numu, at south, it was a volcanic area, but now the volcanoes are sleeping, and Orudels extract rare materials from their cave.