This weapon is an artifact of the felinae. It was passed down from the greatest hunter of one generation to the next until it eventually ended up in the hands, or paws, of Dust when he went off to face the big threat. 
This blade runs along the lower arm of the person wielding it. It is slightly curved, resembling a crescent moon or a claw and bears the signature barbs felinae often use on their weapons. It is said to be so sharp that it can cut any material softer than iron. Thanks to its hardness and the barbs it is actually able to crack open shells of big armored creatures. 
At one point of its history this blade was infused with magic causing wounds caused by it to only heal with the help of magic. This makes it even more dangerous to creatures that aren't able to heal themselves with magic.