The Black Planar Edge is upgraded main-hand specialty axe made by Master Axesmiths who are the only ones who can wield it. The original axe is consumed in the crafting. It gives a higher bonus to critical strike rating and attack power.
This item is crafted by Blacksmiths with a skill level of 375 who also have the Axesmith specialty.
The plans are taught by the Master Weaponsmiths in various cities.