dumb headcanon of the makeup of the Celestial Realm/Devildom I needed to get out of my head. Basically, the Devildom is made of 8 layers with habitability increasing up till Layer 8 aka the Devildom. Layer 9 being Hell/Abyss/Nothingness because the ground collapses in S2 so there has to be some kinda space for things to collapse into. The celestial realm being the way it is based on nothing then I think it looks cool/I play FFXIV/the term "I'm on Cloud 9". It has similar habitability of the Devildom but instead of being because of hostility of environment it's because of sparseness of actual land. It's not pure clouds but islands in clouds. Father's personal cloud is No.9 and you can't go there unless summoned. The Devildom/Celestial Realm are connected, so you can fly (or, Fall in Lilith's case) between them if you wanted too (might get shot down or eaten). The Human World isn't connected physically but is connected via dimensional tears so you can walk between them in the areas where it's thinnest at the various portals within the devildom and at Layer 1. Same applies to the Celestial Realm.
