Vorpal Blade (artifact)
Vorpal Swords are ancient enchanted blades with the ability to pass through anything, including walls, armour, and even the world itself. The only thing stopping it from passing through the ground below is the guard upon which it is mounted.
An ancient cache of some six thousand swords was first discovered by the Marcher adventurers in Kalathipsomi around 550 IS, immediately sparking a small war as numerous factions—including the first Aversarian colonists in the region—fought over the control of these wondrous armaments. In the ensuing conflict, the adventurers that armed themselves with the blades were slain nearly to the last man, as it was revealed that the swords harmlessly pass through anything... including flesh.
Over the centuries, vorpal blades have been distributed far and wide as little more than idle curiosities, only valued by theatre troupes and con artists, with more than a few idioms, bedtime tales, and jokes emerging around the phrase 'Cutting like vorpal.'