Yer, the intelligent humanoid species found to exist on hundreds of planets in the present, were once the natives of a planet named Yvern.
Due to a battle between the army of Gods and demons, that occurred long ago, their planet was caught in crossfire, and in a desperate attempt to save millions of lives, the Celestial Empire of Heaven separated the survivors and randomly sent them to habitable planets, across the galaxy.
As a result, a batch of a few thousand Yers ended up on this unnamed planet, only to realize that the planet was already ruled by an existing intelligent beast-type race called the Aeni.
At first, it was all about survival.
As time passed, the nature manipulation techniques that were passed down the generations and further improved by the descendants made it possible for Yers to claim a share of the land as their right too.