I'm at level 60 or 61 now.
I got screwed in world 2. I beat the boss of 2-3 and returned to the nexus, and discovered that my world tendency for that area was black, and I have no clue why. The only bad thing I've done is accidentally hit the vendor, but it wasn't even enough to kill him. Meanwhile, I've co-op'ed the area with people a number of times. Mostly dying, but still, the intent was there lol.
I have never once used the black stone, so wtf?