The Atsah are a group in Magical Girl Policy. They were a Native American tribe that, thousands of years ago, inhabited the area that would later become Kessia City. There are no records of their existence, but through visions the Spirit Guard learn of them as the builders of the Standridge Hill Stone Circle as well as the earliest humans to have made contact with the Ardent Empire and employ empathokinesis.
The Atsah were at a technological level that was standard of their time, possessing only simple tools such as hammers. Through visions granted to them by the Empress, however, the Atsah were taught the secrets of empathokinesis, an ability that allowed them to build the Standridge Circle, a structure that would be impossible to create with their tools alone. They were unaware of the full scope of empathokinesis or the true identity of the one in their visions, as they were taught only what was necessary to build the Circle, which they were led to believe would attract the "gods" in their visions.
During the Ardentia Civil War, the Empress made contact with the Atsah through visions and posed as their gods. Through these visions, the Atsah were taught empathokinesis, and at their benefactor's behest began building a stone construct said to have the power to draw their gods to the area. In actuality, this was a set of empathokinetic foci called a gateway, which when linked to another gateway in the Ardent Empire, would allow travel between it and Earth so the Ardentia may escape their doomed world. The Atsah completed their gateway near the war's end and the Empire's warp there became its last remaining gateway, so the Empress planned to flee to Earth so the Empire may be reborn on the backs of the early humans and Earth's wealth of resources. Due to sabotage by the Princess's team during the final battle for this gateway, the Empress's plan was foiled and only a gravely wounded Platicore managed to warp to Earth.
Over time, the Atsah died out and took the secret of empathokinesis on Earth with them, and their domain would later become the site of Kessia City. With no records, the Atsah were lost to history, with the only remnant of people existing in the area at that time being the gateway, now known as the Standridge Hill Stone Circle. The structure confounds researchers due to predating records of tribes moving into the area as well as the tools necessary to build it. The Spirit Guard learn of the Atsah, however, through visions of their Ardentia predecessors. Though the Atsah are lost to time, the impact of the gateway they built can be felt even in the modern day, as the Standridge Circle's powers have unusual effects on Kessia City, such as the place attracting those with high empathokinetic potential.