User blog comment:Blood Reaper/Skyrim Dawnguard Trailer/@comment-101.160.192.77-20120602024838

Kind of worth noting, the Sun, and stars might I add, in the Elder Scrolls series are actually holes to Aetherius, created by Magnus and his followers when they decided they would take no further part in the creation of Mundus and escape. More specifically, when Magnus created Mundus, he was disgusted by it, so he fled, tearing a hole through Oblivion, which became the Sun. Some other et'Ada decided they would follow, the holes they tore through become the stars. And finaly, as Aetherius is meant to be the origin and source of magic, the sun and stars are ways for this magic to be able to seep into Mundus, in various forms which can be utilized in various ways. Thus, the sun and stars are the source of magic in Mundus.

So, according to the narrator, the vampires are in effect blocking the biggest hole to Aetherius, the biggest source of magic in Mundus, and thus partially blocking out Aetherius itself. Wonder what the effects of that might be, and how perhaps Molag Bal (I posted a theory on a possible role of his in the DLC, look down in the comments to find it, as I can't be bothered recounting it here) could be involved in this.