>the black shard is a piece of the black knife
>it's the only weapon that's the same in both the light world and the dark world
>this implies that the roaring knight's weapon is a real thing, not just the dark world form of a sword or a bat or something
>the knight can spontaneously manifest this weapon, and adopt it into its form when it shapeshifts
The longer I think about it, the less likely it seems that the Roaring Knight is just a disguise/dark world form of some lightner.