Does debuff stack?

Like papa pixie darkness-ed me, and before it's gone, he uses it again, does it stack on top of the first one(timer wise), or start a new one, or it won't even work at all since the first one is not gone yet?

On most debuffs the timer cannot be restarted until the first one is over, so he can caste darkness all he wants, you're still gonna get out at the end of the timer. The only thing I know that goes around this is Rellik's stungun, since it just keeps reloading the timer every time he hits you with it.

Okay thanks.