And yes, I decided to become a bastard by killing the Mara priest as guided by the Daedric Prince of Dreams.
First time, he destroyed it, but then I figured - "Why do that? What do I care if some NPCs have bad dreams when I can get more powerful Daedric artifacts?!"
But anyway, I'm not seeing the effect of the weapon. Though, I have only used it once on the Battlemage, but as I said it didn't seem to do anything.
Info?