Lord Zack's Planescape
This is the plane of law touched by good, and home to the Faction known as the Harmonium. It is a peaceable place where laws bring about a ideal state. There are two known layers Abellio and Buxenus, and used to have a third, Menausus which has since become part of Mechanus. Local laws regulating travel have stifled exploration of Arcadia, thus it has been hard for explorers to find any other layers. The loss of Menausus has only exacerbated this problem, given that many portals that would have to lower layers would have been on this one.