» Mon May 28, 2012 7:51 pm
When you do the quest to turn the star black, *something* escapes. Curious? Go try it again, if you've got a save near there. As you wake up afterwards, you'll find a red "Hostile" dot on your compass, and you'll hear something running off. I haven't managed to catch up to whatever it is, but I imagine it can lead to further consequences later.
Really, though, the Star is largely a novelty. Even black soul gems are extremely easy to obtain and relatively cheap in that via alchemy, smithing and enchanting money is largely irrelevant, make a bunch of enchanted daggers, then trade them for black gems. The shifty fellow in the college sells them, and always has at least one for sale, and they're less than 1000g (empty soul gems are always pretty cheap).
So, yeah, the Black version is better, but it doesn't really matter. It's a useful artifact, but not spectacular.
As to how it came to be in that mages possession? The Nerevarine has been dead for a very long time now. Who knows how many hands it's passed through.