[@Draco Dei](/images/55375#comment_158259)
In my head, Nightmare is more or less the opposite of Luna. A dark starless night filled wingth monsters and dangers. I wont claim that her mane being starless was intentional, but I found it quite fitting and with her smoke trying to blend the stars out fits even more into it. Also, the picture would be quite "overloaded" with her having stars in her mane too.
In my head, Nightmare is more or less the opposite of Luna. A dark starless night filled wi