Dark Axe
The reward from the 
Reaper replaces the 
Great Axe with a
stronger axe for gathering resources and fighting.
Mechanics
Section titled “Mechanics”Missed swings count toward the bonus attack. Switching away and back preserves that progress; the Reaper upgrade starts a fresh count.
An ordinary tree hit gives 
50 wood; a bonus
hit gives 100 wood.
Stones and gold mines give stone and gold instead. Nearly depleted resources yield less.
Comparison
Section titled “Comparison”
Base damage is higher against players, zombies, structures and resources. The attack rate, special and speed while held stay the same as Great Axe.
Obtaining
Section titled “Obtaining”Reach Great Axe at level 9 through the weapon tree, then have the Reaper kill credited to you while alive. Great Axe must be in your inventory, but another item can be equipped. Your projectile or turret can supply the kill. Earlier damage or proximity alone does not grant the upgrade.
The kill also grants Dark lifesteal.