The raw material of "slag" is the souls of the people I have killed, the remnants after being burned by flames. Because it is waste that can no longer be burned, it can also be seen as a substance that will not change no matter how it is burned.
Strictly speaking, the "slag" that remains after I became the Great Impermanence can still be further destroyed if taken and burned again. However, this process is more of a refinement than destruction, and what remains in the end is still the black "slag."
These numerous pieces of "slag" may seem like useless garbage, but that's not the case. Precisely because they can withstand the destructive power of my flames, they can also be viewed as materials robust enough to bear my flames. However, their overly strong resistance brings another problem, which is their stable nature makes them difficult to refine into magical weapons.
