Blade of Thirteen Dominions

The trickster spirit of this sword seeks to confound the greatest minds of the foe.
Pick one of the bearer's melee weapons to be this. Allocate wounds inflicted by this before allocating any other attacks made by the bearer.
If 1 or more wounds are inflicted on the enemy unit being attack by this, then subtract 1 from hit rolls made by attacks from that unit until the end of the phase.