I also totally forgot about subterranean realms!

We can simplify by saying you guys own your coordinates from the sky to the planet core. Consider subterranean realms to be like "mineral rights" -- you got them to share or use or sit on as you please. We won't have signups for overlapping depth zones. I think that preserves your right to your own zones of arcane and divine magical powers.

Now my realm of Bardu definitely has some drow in the central mountains, but I'm not really big on going into their empire in depth. Anybody who wants to design a drow realm on my turf let me know and I'll share some backstory -- the Matriarchy of Armatta are descendants of escaped drow slaves. I also have some dwarf kingdoms in the same desolate mountain range so if subterranean stuff is your thing I'm glad to share with you.