Okay so in Dawnguard you supposedly side with a vampire who wants to block out/destroy the sun correct? In advanced vampirism the sun hurts you and is generally, bad. So could it mean that if you block out the sun it will affect the main game? Such as all of Skyrim stuck in an endless night, or if it will not affect Skyrim after completion at all. (Having the sun out of the way would be helpful for vampires....)