I’m still world building. D&D is full of loads of idiosyncrasies I want to drop or re-evaluate. I pretty much dropped the planes in favor of the super-simplistic omniverse cosmology. It works much better as a starting point and fits easier with my adjustments to the undead.
I took a look at medieval bestiaries and mythology for inspiration. Now my setting has vegetable lambs and barnacle trees, and manticores are considered wild beasts instead of unnatural monsters.