This is not a feature of the world story we are creating – we are interested in the peoples who live on the five world-creatures and the lives they lead – but for some background/bigger world context:
The space the world creatures are moving through is a bit like an ant-farm or mini-zoo kept as a hobby/experiment/teaching tool by an alien child. That information is so beyond the ken of the peoples (and the world creatures they inhabit) that they are not aware of it at all. The child-owner of the universe-toy has trained each of the world-creatures to follow their particular paths over time (using food) and that’s why they repeat their chosen routes. The physics and science of their world is not like ours and hence the world-creatures can move through their universe-toy in a 3D fashion without any apparent roads/surfaces. The child-owner occasionally adds new animals (like Remum) and other random elements (like the train). Time moves differently for the child-owner, the creature-worlds, and the peoples.