How the dreamworld works is each world created by Lili's subconscious. Each world is lead by doors that only Lili can find. Each world reflects Lili emotions, trauma, inspirations, aspirations etc. Only Lili can open these doors. Even dream walkers have doors that can lead to their own worlds if they slowly start to become influenced by the dream.
In a way these doors can help and guide or trap and create anguish. Some doors are connected to the same world and phases and some are not. Each dream dimensions leads to a new phase and a new connection.
Doors can be easily design or have complicated design depending on the world, These doors can be in closets and cupboards, windows and even paintings.
I would have dreams as a child about jumping into different dimensions based on the painting I went into. The catch would be never to disrupt the narrative within these worlds or the entire dimension will come crashing down with you in it.
this is a very similar idea to what I'm trying to do in R.E.M and will be further explained in future rewards