I am working on a map, and this happens with all maps, but this one especially since there is a much bigger variety of elevations than most maps. (in fact a ~2500 ft/762 m range) How can I get rid of it? It is mostly seen if you are higher up in elevation or are close to the edge of the map. And at the top... (the top part is not finished yet, but players will still see that ugly black thing...)
That can't be removed afik but the color can be changed to sky blue or whatever you like. This is done in the editor somewhere.
You could always add your own skybox to make "fake" terrain. Or literally create fake, low-lod terrain like is used in Canyon of Speed.
I'd really like to know how to fix this or at least change the black to some light blue. I do not want to increase fog density, however.
Check the 'canvas clear color' setting under level info. It isn't 100% effective but better than nothing. Some trickery with the fog can augment the blending effect a bit. Ultimately you will want a properly crafted distant terrain, skybox or a waterplane to hide this completely. I haven't really paid attention to this lately but some maps appear to have it and some don't so I'd like to think the devs have figured out a way to at least make it flat and less of an eyesore.