It's been a while since I last partook in a contest but I'll give it a try. Here's the first draft for the story:
Inspired by Velen's and the Draenei's escape using the Exodar the Buring Legion™ sought a way to both track them across the Great Dark Beyond and to have the means to invade unsuspecting worlds that cannot be reached by portals.
The answer to this challenge are the world corrupters; giant dimensional fel powered ships that roam the Twisting Nether. A corrupter is a sight to behold. It seeks out places brimming with life only to feed that life into the fel that is needed in order to funnel the very Nether itself down from the sky to the corrupter. This allows the Legion to open up it's numerous portals to other Legion worlds it brought with it to open up and let the invasion begin.
It's essentially Independence Day but with demons. And in heavy metal. I'm not sure yet if I want to show the thing in its entirety, or just a cutaway or something like that. It depends on my time. What I envision is a giant burning Burning Legion space ship with Iron Sky Götterdämmerung inspired moving parts, armed with cannons that rain down infernals (in case you ever wondered from where in the sky they're coming from), home to a vast demonic army and factories for fel reavers and other weaponry.