"An axe imbued with magic fueled by the destruction of the unholy. With every victorious blow against an undead creature, its power grows. Arkay warns it's baneful charge abates with each dawn. Something to keep in mind, I suppose."
The unique enchantment gives an increase to the Sun Damage capabilities the weapon already possesses, as every undead being that is killed by the axe will add to the power of the axe's Sun Damage enchantment.
The maximum power of the enchantment is achieved after one hundred kills. The axe's kill count will not reset if it is tempered at a grindstone.