A Fire and Darkness
Up and Down
The basic thing to remember is that darkness floats.
Any sufficiant mass when encased in darkness will try to repulse off of any other mass. What that means in effect is that there are flying mountains, flying trees, and if their owners are very clever, flying castles.
It also means that sailing over land is the fastest and most cost effective means of travel. Rather in fast schooners or heavy barges pulled along by beasts of burden. the “sailboat” is the primary means of travel.