The Plane of Whatever It is, I'm Against It

No one is quite certain how the Concordant Opposition came to be. It is quite possible that some soldiers of Law and some warriors of Chaos tired of the endless battle of natures and paradigms and came together in that consensus to make another alternative. Others believe (or hope) that it is the place where the last fragment of the Godhead exists. a strange loop of dreaming God unconsciousness, a bulwark against a schizoid multiverse. People in the City of the Sigil, in particular, like this idea.

However it came to be, it stays because he serves a purpose. It's the phase boundary between not only Law and Chaos but the other syxygies which emerged from their conflict come together. It is the place of concordant. Of course, it actively resists being incorporated into any camp (though they all try). It is a place of opposition.

Across it's expanse none the Powers hold sway, yet no where are their philosophies more discussed and debated. There are groups of evangelists and missionaries from other Planes working to convert travelers, though these all die out eventually, either in conflict or by loss of faith. The plane does not mock, but it is actively indifferent.

At the edge of these Outlands are the Border Towns. Their appearance vary from town to town, but they control the flow of traffic from whatever plane is on the other side. All are fortified, no matter how benign the appearance of the Plane on the other side. Indeed, from the perspective of the Opposition, the most benign are often the most dangerous.