All things possessed yin and yang.
Just as beginnings were always followed by endings, the opposition between spiritual energy and magecraft represented the ebb and flow of life itself.
Like the positive and negative poles of an electric charge, spiritual energy and magecraft were both transformed from vitality. Whether it was the magecraft of the Great Source or the Spiritual Energy of all things in the world, they were fundamentally the same thing.
Therefore, whether human or demon, exhausting all their spiritual energy or magecraft would not result in death. They could simply wait for it to recover slowly. Losing yang left yin, and losing yin left yang. Neither meant that their vitality had been completely exhausted, so naturally they would not die. Only when both spiritual energy and magecraft had been severed could their vitality no longer be maintained, because that state had nothing to do with either life or death. It held the same meaning as nonexistence.
However, although magecraft and spiritual energy were powers that reached the same destination by different paths, their properties were opposite. To a certain extent, they could replace each other, but to distinguish them more clearly, people generally did not possess both powers at once. Otherwise, exhausting them both would mean death.
Thus, human Demon Slayers such as shrine maidens, Psychic Ability users, and Curse Users all used spiritual energy, while demons, Witches, and Magi used magecraft. The former wielded curses, while the latter wielded magecraft. Even though spiritual energy and magecraft could replace each other to a certain extent, that replacement was extremely limited.
Luo Zhen had once used magecraft in the world of Tokyo Ravens in place of spiritual energy to generate curse power, thereby wielding curses. He had even absorbed spiritual energy from Hokuto and the Valkyries to use