Help me understand Bloodspiller

[AncientCrystal]

I swear I've read this tooltip a hundred times and I either forget how to buff it, I misread it, or it just makes my head hurt lol.

So if it wants you in GRIT to buff it, does that mean if your in DARKSIDE as well that doesn't buff it or do you have to be in GRIT alone?

And how the heck do you even pull this off cus I can't think of any times when I'm not using Darkside so this move baffles me