All right, read this during lunch break and thought I'd drop a review!
I like the attention to detail. You've attempted to paint a scene with enough details that the reader can imagine it themselves. I also like that you were blunt with your descriptive details, and didn't delve too much into poetic devices.
There were a few run-on sentences [For example, Inferno, a flaming abyss filled to the brim with berserk creatures of darkness. Ruled by a big red monster with a forked tail, who tortured souls with maniacal laughter.] This should be one sentence. The sentence starting with 'ruled' is dependant on the first sentence - it cannot stand alone. OR you could write 'It was ruled by a big, red monster....]
Also some bizarre sentence fragments: [What a soft blanket he could feel under his tights, warming the exposed skin as well as the dark feathers streaking up them]. This really doesn't make much sense and feels odd reading it out aloud. You could try: He could feel the blanket beneath his thights, the soft fabric warming the xposed skin, as well as the dark feathers streaking up them.]
Fortunately, these are minor errors and are really easy to fix. Also, you probably shouldn't start sentences with 'and'. Your sentences would work much better without it.
But yes, good detail, and quite visual. Interesting characters too though I can't really comment too much on them yet since it's only the introduction. It's obvious you'e gone into a lot of thought about your birdfolk - they are unique and that's good to see!
Good job ^_^