Amnar is an alliance of seven city states across several continents on a planet called Amaresh. The seven city states emerged after the end of the "Gap War".
Five empires had worked together for over a thousand years to control a vast stretch of territories. They fought a series of wars over control over a technology that would enable the leaders of those empires to become gods.
The effect of these wars was the displacement of millions of people, the destruction of the environment on a global scale, widespread enslavement and conscription, scientific experimentation to develop new technologies in the pursuit of the ambition to harness the power of the gods.
Accidentally, one former slave fell into the God Machine and was the first to connect with the gods to become one herself. This was Isha. She changed the tide of the war by inviting refugees, slaves and former slaves, and others, to find sanctuary in the former territory of one of those empires. These people became known as the Hundred Thousand, although there were probably many more.
To protect them, Isha called upon five tribes—also known as nations—from around the territories of the five empires, to unite under a single banner.
In order to stop her, the empires ripped open holes in reality itself, known as "Gaps". The first opened in the cavern where the Hundred Thousand were hiding from the empires' armies.
Isha and her supporters were eventually able to defeat the empires. However, it was at incredible cost. Seven gaps had been torn open, throughout the world. These holes led through to other, terrible places that released awful monstrosities that poured into the human realm.
The Hundred Thousand, the members of the five nations, and other survivors came together under the banner of a new civilisation called "Amnar".
Its intended purpose was to protect the rest of the world from the creatures that came through these unstable tears in reality. Each of the cities surrounds a gap. It's an unusual setup, since most cities protect inhabitants from outsiders; Amnari cities protect outsiders from the gaps at their core.