Skull and Shackles
Altered Vorpal Rules
Variant Vorpal Rules: Vorpal weapons allow a user to deal more damage than normal via a supernaturally sharp edge. When attacking with a vorpal weapon, the player rolls an additional d4 and multiplies the base weapon damage by that amount. In addition, vorpal weapons increase their critical multiplier by 4, threat range by 1 and always bypass hardness.
For example, a Vorpal longsword would do 1d6x1d4 base damage, have a critical threat range of 18-20 and a critical multiplier of x6