Is Vorpal Strikes supposed to qualify as being able to do slashing damage for Sting of the Ninja or not?
Sting of the Ninja
Weapon Stance: You poison your weapon with a secret mixture. While you are centered, piercing and slashing attacks you make deliver a stack of Ninja Poison on critical hits. Shuriken apply this effect on damage instead of on critical hits. Unarmed combat requires a set of handwraps for this to apply (as well as a way to deal piercing or slashing damage).