He’s Smithing?

The Innate Fetal Poison which had plagued him for over a year had disappeared without a trace. However, remaining in its place was a ball of black smoke.

This bundle of black smoke wasn't too big, roughly the size of a fingernail. It sat quietly in the midst of his meridians, not moving at all.

I have no idea what it is, but it's unlikely to be anything good. Let me see if I can get rid of it!!

Zhang Xuan continued to channel the black flame into his body to burn the ball of black smoke, but it didn't seem to faze the ball of black smoke at all. Even the Empyrean Heavenly Flame, which boasted the ability to be able to burn anything down, was completely ineffective against it!

What in the world is this ball of black smoke?