The victory maps are outdated. You don't need central Arabia to win.

Quote Originally Posted by Olaf The Great View Post
The city "Terhazza" of the Province "Eremos" is what you'll have to conquer to "own" that area, it's in the very Southwest corner of the map.
Except that you can't conquer it without cheating (as the city can't be reached) and that you shouldn't anyway because it is used to place script markers.