Hey there,
I like this; nicely composed. However, even though it's a loop, I think it can use more movement. It's all kind of one level right now, and I feel like there should be accented moments (maybe some brass stabs, cymbal crashes, low string ostinatos?) As it is, I feel it's a little two mellow for a final dragon boss. It's ominous, but it doesn't get my blood rushing as much as I want it to. Good start though, and I think with a little more work it'll get there!