Apart from being the creator of the Painted World of Ariamis, very little is known about Ariamis. While it was originally believed that he was tasked with making a prison for Crossbreed Priscilla, she later reveals that he created the painted world as a sanctuary for the lost souls of certain creatures.
Over the years, countless other forlorn souls have wandered the lands. Eventually they discover entities who tell them about the painted world, and how it welcomes those with no home. They also relate the forms of the Painting Guardians, and of Priscilla, who is the Mistress of the Painted World.
Eventually the world of Ariamis began to rot, and so a new painter was chosen to replace his rotting world with a new one, so that it could make a better home. All the rotting residents died, likely including Priscilla, and it is unknown if Ariamis died with his world.