You have a very good feel for meter and rhythm. There's some good imagery here, too. I like it. Good work.
There were a couple of times (the second stanza and the last) where you changed imagery and then returned to the previous idea/image in the next line. This jarred my focus from what I was reading. I think it might be stronger if you stayed with the same idea through the whole stanza.
In stanza 2 you switched from specter to dark clouds pulling back the covers, then back to phantoms. What if instead you described it with a ghostly or skeletal hand pulling back the covers? (Or whatever image you like)
And in the last stanza the image shifts from a battle to the stormy eye, which makes me think of a hurricane, then back to slaying the creature. This one especially pulled me out of what you were trying to say, because I was thinking, "You can't kill a hurricane."
Just a suggestion. Poetry is very subjective.