On the CKII Wiki, it says that portages (in the adjacencies.csv) are required to run. What does this mean?
I'm creating a map from scratch, and I want to get a functional map first before I add fancy stuff like adjacencies, but I don't know if I need to include a new, mostly blank adjacencies.csv or if I can just copy over the vanilla one.
Also, is the continents.txt file required. As it says it doesn't do anything, does it need to be there or can there just not be one?
You need to have a valid portage in your adjacencies.txt or the game will crash on loading. The adjacency can also be between provinces that aren't actually on province map, but are in definition.txt.
You can ignore continents if you wish, but continent is valid condition in scripting.