Whether a samurai sword or a kitchen knife, a physical blade has these parts:
In comparison, a metaphysical blade has these aspects:
Substance of nothingness
The cutting edge clears the area; separates the structure. It lets us see deeper.
The piercing point is applied at the center. We can make a structure explode, implode or become stronger.
The substance of nothingness is the void left behind by using the edge, or the carrier of energy when using the point.
The interface lets the user connect to the blade and become one with it. It is also the one thing which makes the entire blade usable as a tool.
Let's extrapolate and add some more dimensions to our metaphysical blade. How does it look like? What do we get?
By using only the first three basic parts (cutting edge, piercing point, substance of nothingness), we get the archetype of the all-consuming fire.
By itself, it is extremely dangerous if we apply it unto ourselves.
By applying shielding techniques, we can create an interface which can give balance to the fire, filter it, and allow us use it.
We get the choice to decide what to burn and what not to.