Its very ard to calculate a variable on a shield.
I say if you want to affect shields, give momentum, or +x while they have a shield or destroys shields.
Why is it a Darkness Weapon?
How does it work against Wings, or Phase Shield or Fire Buckler?
The concept of damaging armor and shields was what I was going for; we discussed the history of that in chat. I could simply do a group buff, but its also in the element with Eclipse, which is a bit redundant.
Darkness seems to me to rely on sabotaging the opponent's efforts, through cards such as Steal and Devourer. A weapon that reduced their ability to defend themselves seemed appropriate.
Any non point shield gets a percentage nerf, so that Wings would only work 90%|80% of the time, same as Phase Shield. Fire Buckler and others that don't block damage are like shields that block 0, and 0 minus 1 is negative 1. You can't block negative damage, so that means its like adding to your creatures' attacks.