The Empire began as a confederation of tribes in the region where the Imperial capital is today. The tribal people of the area were united under one banner by the Caelia tribe by force; the instrument which enabled them to do this was red magic, which was believed to have been a gift from the Caelian god of war. The other tribes didn’t have access to the magic which the Caelians were quickly mastering, and it was not long before the Caelia tribe was the main power in the area. They formed the Kingdom of Caelia and proceeded to lay claim to most of the northern part of Arkadia. After spreading their people across the land and conquering any other tribes they encountered, they turned to the south, past the mountains.
They encountered the Samsaran Empire, a people far in advance of the Caelia. The king of Caelia approached the Samsarans peacefully and set up good relations with the Samsara, who shared with the Caelia the secrets of their advanced magic; this was when green, purple and blue magic was discovered by the Caelia, who began combining the new knowledge with red magic to create various pieces of machinery. Over the next few hundred years this secret technology included very powerful weapons of destruction and war; meanwhile, the Samsarans, the benefactors of the Kingdom of Caelia, remained blissfully unaware of these secret projects and even of the fact that they possessed red magic.
And some geography:
Arkadia is the homeland of all the major factions of the world. The Empire of the Three Suns was born here and in its golden age, it controlled the entire landmass. Its major geographic features are the Name mountain range in the centre of the continent, splitting the liberated territories of the former vassals of the Empire, the Republic of Samsara, and the Empire itself. The pass between these two countries has always been of strategic importance, and neither side controls it completely.
Another geographic feature is the swamp of Words Here, at the southeast tip and surrounded by mountains. It is a major source of alchemical ingredients, and is accompanied by Fort Pantano, the settlement and stronghold built by the Empire while it controlled the region to extract the rare flora which thrives in the swamp.
The vast forests at the southwest edge of the continent hide most of Arkadia’s remaining tribal peoples; rumour has it that they possess ancient and powerful magic which are imbued in the form of tattoos. The dark woods are uncharted, and very often explorers wind up dead; there are rumours of some kind of evil fairy kingdom hidden in the forest which does not take well to outsiders. No evidence, however, has been given to support this other than hearsay.
Hitori is a barren wasteland, the entire region being choked with the ash of the numerous volcanoes in the mountainous landmass. What little is known about the place is that it is the home of many dragons. Dragons are almost extinct in every other region of the planet, but they thrive in the lavatic land of Hitori. Everything else about the continent is purely conjecture; for example, it is believed by some that this is also the home of a king’s ransom in dragon’s treasure and undiscovered minerals.
Aditora is a mostly uncharted land of monsters and savages. The island, noted for its sickle-like shape, is almost entirely forested, to the point where an incredibly dense rainforest resides in its southern part. The continent is webbed with many rivers, none of which have been mapped out; the primal wilderness is anything but hospitable to humans, and any attempts to colonize it have been confined to the western tip of the island, where a small trading post has been set up in an attempt to acquire the unique bounty of the beastmen who reside in this place. What little interest the trading post has attracted has mostly been positive, much to the relief of the colonists, who have been able to sell off the interesting alchemical ingredients and materials for great profits.