Because he saw the edges of the scratch on his breastplate turning red.
That red was not the red of blood, but something deeper.
Around the point where his armor had been cut open, a layer of fine, blood-red cracks was slowly spreading across the metal surface, like porcelain beginning to shatter from within after expanding and contracting in the heat and cold.
"What's on your blade?"
Blood Slaughter lowered his head to look at his breastplate, genuine confusion lacing his voice.
"On this humble monk's blade..."
Blood Chan Zi took three steps back, widening the distance between them once more.
Blood still dripped from his cleaver. The line of blood-colored scripture on its blade had absorbed the killing intent from Blood Slaughter's axe edge and now shone more than twice as brightly as before.
"...is this humble monk's own karma."
"For every person this humble monk kills, their karma is borne upon this blade."
"The karma of three thousand seven hundred and twenty-four people, layered together, is the edge of this humble monk's blade."
"Where this humble monk's blade has scratched your armor, karma will seep in and slowly spread along the armor's patterns."
"At the fastest, half a cup of tea; at the slowest, one stick of incense. Your heavy armor will begin to collapse from within."
Blood Slaughter listened in silence.
His expression could not be seen behind his face-covering helm, but his scarlet pupils contracted slightly before quickly returning to normal.
Then he raised his right arm, held the Double-Edged Great Axe across his chest, and extended the iron-gauntleted fingertips of his left hand to dig fiercely beside the scratch on his breastplate.
His iron nails sank into the armor's surface, tearing off a small blood-red fragment corroded by karma.
He looked at the fragment, then