A triad of suns seems to form an almost perfect equilateral triangle in the sky of this otherworldly scene.
I had a bit of a go with render times. At first I had used default node as the brightest sunlight and was getting up to 2 hours. After fiddling with various clouds and settings I thought the atmo was the culprit until I disabled it and used a new sunlight node with the same strength. 20 minutes or less for this and other test renders.
Anyway, I'm kind halfway satisfied with the result.