If you explore the skyway around the desert, try turning to look towards the desert. At certain points (IIRC one is near the NW corner, and another is along the E/W part of the skyway somewhere just north of the great southern tower) you will see "islands" of land floating above the desert. You can use the teleport spell to get from one to the next, but save your game first, because you can't tell how far away they are.

On some of these, you will find locations which give you some options. Again IIRC, two of these are gold and promoting one of your characters - I seem to remember that there is a third, but I've forgotten what it is. (I think I first gained access to the skyway from the top of the great southern tower, but it was a long time ago and I can't access these games at present, so I'm not sure of that.) Incidentally, I've never seen these "islands" on any map.