What does the Enchantment Vorpal do?

The Redpower2 mod for Minecraft removes the default chance of a mob dropping its head, and instead adds the Vorpal enchantment. When killed with a Vorpal enchanted weapon, mobs and players have a chance to drop their head, increasing with a higher Vorpal level. Unfortunately, this affect does not work on wither skeletons. The Vorpal enchantment also gives a chance for your attack to deal a large amount of damage.

Vorpal Enchantment: (RP2)

Type: Weapon

Vorpal Levels: 1-4 ; Each rank increases the likelihood of the effect.

Effect: Beheads the enemy, killing the player or mob and dropping their head. Does not seem to affect Wither Skeletons. Note that this is a 1-shot kill chance and is a powerful enchant.

It increases the chances that a mob drops its head. It comes from the RedPower2 mod.