The Orbus Barrier (オルバース界面?) is the divider between the worlds of Inferia and Celestia in Tales of Eternia. Its main feature is the Seyfert Ring, and it is the location of the final dungeon in the game, Shizel's Castle, as well as the bonus dungeon obtained upon completing the game, Nereid's Labyrinth.
As of the beginning of the story, the Orbus Barrier has shown signs of weakening because of the dark matter contained within the Seyfert Ring, an indication of the Grand Fall. Farah Oersted notes that the color has changed in the first scene. The barrier shows several signs of deteriorating as the story progresses, such as a causing a landslide when the party is at the Rasheans River pier. In order to prevent the Grand Fall, Reid Hershel and his companions are forced to destroy the Seyfert Ring at the end of the story, causing the two worlds to separate and presumably destroying the Orbus Barrier in the process. Late in the story, the Van Eltia gains the ability to travel across the Orbus Barrier via Aifread's Relay Point, whereupon it appears to be a thin layer of clouds, through which the surface of the world below is faintly visible.