6. Thick, congealed strands of necrotic energy start leaking in to the Material Plane causing anything the tar touches to wither, die, and reanimate. Brave heroes must find the source of the spill of negative energy and plug it before [the main world of your campaign] completely plunges into the Negative Energy Plane.
Oh good, something to distract me from studying for finals. If I fail, I'm blaming the GRC team. But, seriously, this looks great. I can't wait to look through it in more depth. Great work, everyone.