PolyHero Rogue: 5d6 Swords - Nightshade - Rules of Play says:
Sneak Attack. the classic rogue move, emerging from the shadows and inflicting a barrel load of damage on an unsuspecting foe! Now you can load up with a handful of d6 blades and sneak attack in style. (d6 swords are in general a very versatile dice, and suit many other fun applications.)