Feathered Weapon (5e Equipment)
From D&D Wiki
Weapon (any), common
This weapon was specially enchanted to weigh almost nothing in the hands of its wielder, but seems to still have its normal weight and heft by those that it strikes. This can make a weapon enchanted this way act as if it is truly so light, even when considering momentum and drag, but allow it to be quite brutal against foes.
Light as a Feather. This weapon has the Finesse property, even if it normally wouldn't have it. It also loses the Heavy property if it has it. Unless it would normally have the Finesse property, features and effects that require using a weapon with the Finesse property (Such as a Rogue's Sneak Attack) can't be used with this weapon by this enchantment alone.