The Nature's Scythe is a very rare drop from the Nature Guardian.
As a melee attack, the Nature's Scythe will do around 7-10 damage, around the same as a Diamond Sword.
Throwing the Nature's Scythe will go through mobs and destroy leafs and plants, doing 10-14 damage (5-7 Hearts) per hit, however throwing it will consume 200 Mana.
The Nature's Scythe has Soulbound I by default on it. It is not enchantable at an enchanting table.