ForgeWorlds™ are the many faceted versions of Earth that fractured off from different points in its history or changes to its core functioning rules.

In some worlds, it is just a historical shift.  In others, it is a complete shift of reality changing the rules of physics, genetics, supernatural and the elements themselves.

In one world, there is no Earth.  In a far removed future the Centrifuge exists where the Earth once laid orbit.  It is here that the various ForgeWorlds™ are monitored, quarantined from one another and even policed.  Forge Agents quietly intervene where needed and visit these worlds to try and curb or even reverse the effects of the Decay – which triggered these various parallel earths to begin with.