Ok real quick about “Earths”. This information mostly comes in handy when it comes to understanding the Train and the humans in Ileosa. The Train can only take humans and only from earth.
There are different versions of earth and they have their own little codes. Saul being from E-139, Eimantas being from E-404, Michael being from E-616 etc.
Earth versions are a play on the idea of alternate timelines, except in the Ileosa universe, not every action can create an alternate timeline. Earth versions are distinguished from one another through a key event that leads that version through it's own distinct development. This event can be small or large, it can bring about changes immediately or maybe in hundreds or thausands of years. Yet that key event happening alone is what creates the alternate earth version.