Stygian Blade
What is up with the powers known numbers in parenthesis?
Also, the powers known don't make sense to me. You need bonus PP to gain powers known at level 4 even though the class grants you PP at that level? And why do you need bonus PP to gain powers at levels 8, 11, and 14? Also, why does the progression stop at 4th level powers?
Why is Stygian Curse a maximum of 3/day?
Stygian Shadow stacks with itself as written. Also, this is a commoner killer. Way too powerful for level 4 as written. I'd go with something other than temporary negative levels honestly. Maybe saving throw penalties or something.