Mightyena
Fur as black as a moonless night}
Eyes glinting red like the dawn}These two lines masterfully picture the majesty of a Mightyena. I see an obsidian black werewolf like being lurking at midnight. Bravo!
Curving long sabers called fangs glisten in the moon}Let the reader decipher it as a simile instead of pointing out the obvious. Use "as" in lieu of "called", and use "beneath" rather than "in" to accentuate the luster of Mightyena's teeth.
Ears pointed and delicate}Those who know what a Migthyena is would be able to visualize this already. Try to use some adjectives instead in order to cement his characteristics rather than his features.
Claws sharp and long}See commentary on line #5.
Tail held high like a flag}See commentary on line #5.
It runs quickly yet gracefully}The words "runs" and "quickly" have meager amounts of poetic value which ensues the impact that "gracefully" would normally project. Try to be more consistent by adding equally potent words.
Its eyes can see what we cannot}See is a very shallow word, you could either replace it, or rephrase the entire sentence. Make sure to maintain its meaning though.
The ears can pick up the breath of an insect,}Like stated in the previous lines, the word "pick up" lacks the vigor that other options would have. It suffers from informality, so I'd look for a more suiting synonym like "senses".
It can sing a beautiful song to the sky}The word "beautiful" is somewhat over used and has lost its profound literary significance, unless you use a handful of words to compliment it. For the word "song", there are plenty of substitutes which include "madrigal", "rhapsody", "chorus", "ballad", and so on and so forth. Your intention here isn't bad at all though, you did a good job thinking this out.
Mightyena