@ryu23  
Hmmm…four ponies who needed Twilight’s intervention, this nescesitating Nightmare Moon’s escape. That could be!

This is a what-if but if I think about it, has to be Trixie, Sunset, Starlight, and Tempest.

@SD50-2  
Hmmm…it is also seen in the night sky. In universe, it is possible 5g3 author simply put 4 stars because those are 4 very real stars that seem to surround her.  
I’d honestly love it if they were not villains. What if they were friends of hers who aided her or tried to someone endanger equestria after her banishment? Not only would Luna have to face them, but she would have to reconcile having friends from a millenia ago and friends in the here and now.

Also, those four stars are in a book, that’s clearly illustrated in-universe. It’s entirely possible that the artist just put like four or so stars in the drawing to show that the moon is being seen at night or something.

@Eclipse Wing
 
@Background Pony #A546
 
I think if season 10 doesn’t address it, a later comic series will. Unlike season 9, it seems like Season 10 is not currently the last season now that they have switched to comics. That’s pretty normal too, since comic series usually end if they stop selling. ATLA is still getting books and comics.

Personally I prefer the thought that it was a misunderstanding of the “prophecy”. Twilight saved Luna from the Nightmare. The Stars aided in her escape. Fits right in with how vague misunderstood prophecies tend to work.
 
But a concrete answer would be nice.

I’ve been wondering this for a LONG time and hope that the comics at least address it before they end…

@Background Pony #C267  
Yeah…no.

Honestly, whatever those stars were, they already fullfilled their purpose and gone extinct. There’s no point in making stories on starts whose light faded when NM escaped. Probably those stars got too close to the moon’s orbit and gave NM enough fuel to her magic to escape. Is that simple.

Hmmm…  
Perhaps season 10 will explore this?

That is a good question