The Blood Scythe is the item used for harvesting souls. It can also be used to craft the stronger weapon, the Bone Scythe
Cool Crafting Recipe Edit
The scythe is used like any other weapon. It does 3 hearts damage. When you deliver the final blow to anything that is alive, it will try to consume a glass bottle from your inventory. If it succesfully consumes a glass bottle, it will add a Soul in a Jar to your inventory.