Personally, I liked a lot this character. "King Sombra", I liked the way the used a thing that we call here "Spanglish", same as princess luna for example.
Now, on the work... I like it. It was simple, concise and the colors were used pretty well. I think that the best part of this draw, and it's also the part whose caught all of your attention are obviously the eyes. They're "Cool" in one word.
Now... I think the colors of the armor and crown should have been more bright; it's kinda weird to see some glowing eyes, mane and horn but the rest of the colors are a bit dusty. Maybe you're trying to make that effect but it's kinda Odd.
Well... I have to say it, I liked this draw, but i think it could have been better. Keep the good work.