The Terra Ring is a collection of worlds that are Earth-like in some way. Once known as the Terra Cluster, this ring came into existence as a part of a board wide story called the Terra Stabilization. While there are some differences, the main factor of these worlds are that they are almost exactly like our own. The technology level is similar, any fantastic elements within them are generally mundane in their application, and humans - or some variant - are the dominant species. Some of these worlds, though, deviate from our own at either a key point in history, or due to some breakthrough or scientific discovery making how things panned out very different.