King Sombra, a cruel ruler of destruction and hate, almost destroyed the Crystal Empire and almost took control. Although behind this chaos is a father, a loving, but hard father. King Sombra wants his son, Prince Onyx, to take his spot in becoming a ruler, although Onyx doesn't want that he wants to travel and explore Equestria, just like any other pony. Then there is Princess Cadence's daughter, Princess Nomina is the casual air to the throne, but Nomina is curious about this one friend she wishes she could meet, although her parents won't allow it, that friends name is Onyx.
Chapters (4)
Not bad, but a few words of advice:
Your transitions are a bit sudden and short lived. If you're dealing with only two characters, try to draw out their scenes a bit more, rather than establishing extra detail after another transition back to them.
Also, certain details should be expanded upon, like, well, everything about the Shadowbolts (seeing as you gave us next to no info on them), how Sombra is still alive, who these mysterious messengers of The Crystal Empire are and how they and the Shadowbolts found the pair, and I'll stop while I'm ahead.
And lastly, one wrong word choice to fix:
Nomina giggled and complied with her mother, she loved to help her mom with her royal duties, although it wasn't her dream to become air to the throne,
air should be heir
What I got out of the short summary:
one or two complaints, but nothing 2724335 hadnt already said, aside from maybe more commas in certain points, certainly worth following
More please
dat pic
2724335 Thanks for the heir thing
I'm going to be a douche and say, it's heir not air in the description.
I'm liking it, fave and like.
2725672 Yes, yes I know I was having a hard time remembering which it was
but thanks for that 
Doesn't Princess Cadence have a pale pink cost, not a pale white one.
Other than that good job, you're gonna go far kid!
2730186 Come to think of it yes, yes she does
2731971 Other than that itsy bitsy error, good work!
I expect great things!
nice job man to bad I can't give it another like.
Also i found something:
I think it should say: he though he had lost the shadowbolts.
But besides that good chapter.
It's princess cadence not nomina
Great chapter as always
as always good chapter, there was an error but I think the person before me already said it.
I was meaning to ask do you have an editor or proofreader that helps you?
2738446 Son of a....
thanks for pointing that out
Amazing!!
AHHHHHHH! MY EMOTIONS...TOO MANY FEELS AT ONCE...HEART....THE CUTENESS...UGJVJF TH TH F UH UHJGJGHCGXFXFSFSFJVJBJBJBJF!
sorry if I sound a too critical but i'll go straight to the errors:
you changed from third person to first person in the same sentence.
you keept using the word filly but since you're talking about onyx it should be colt.
You should also separate somehow the battle readers.
Ok all that aside bravo sir, bravo a readers.
Ok all that aside bravo sir, bravo a very good story indeed, although I think the chapters could've been stretched out a little more, but hey thats just me, very nice job with the story.
P.S. sorry for the huge comment.
2749530 Yes the first person thing I swear I cringed at when I found out I did that
and I tried to rush that, colt makes more sense, don't worry x.x
2757478 no biggie, if you ever need a proofreader or editor just let me know :)
2758450 That would be great actually
I like it, good job!
Hmmm a fish pun, eh? Well I really enjoyed how the story HOOKED onto me and REELED me in.
I would have a fish pun, buuuuuuuut I don't so yeah!
THAT WAS AWESOME
I will admit I did not read this, BUT!!!! WHY THE HELL WOULD SOMBRA'S SON EVERY THINK TO NOT OBEY HIS FATHER'S TO RULE THE EMPIRE!! I MEAN DUDE!!! DUDE!! YOUR FATHER WAS MADE INTO TINY LITTLE PEICES BY THE CRYSTAL HEART!!! WHY WOULDN'T YOU OBEY HIM AFTER THAT!!!!
But despite all this I am just a lone commenter so don't be all "You didn't even read it!" up in my ass!(plot)
3907569 Haha don't worry, yeah I see the logic, but eh just sounded like it works within the story ^_^
3956183 Good move.
By the way, filly is for female, colt is for male.