Keychain

A unique weapon with strange potential. It's sister is a thick, large, lock-shaped shield. These weapons are used by specific masters of the monks on AV10, normally those who are deployed by The Celestials on some sort of mission. 
The weapon itself is a large, iron key infused with large amounts of blightsteel. A chain measuring twenty feet in length accompanies it, and monks due to their magically enhanced strength and speed can use this chain to throw the key around similar to a kusuragami. The key is weighted in such that it can smash through most defenses and quick enough that it's not very easy for enemies to track. Several of these weapons are cited as "legendary artifacts" or "anomalous" by various sources.

Hitashi is one of the most famous keychain users.