Why should he kill him?
It was true that never till that moment had he hesitated, by fair means or foul, to remove an enemy or rival from his path.

He had been brought up in this teaching; it was part of the education of wizards to be merciless, for they reigned by terror and evil craft.
Their magic lay chiefly in clairvoyance and powers of observation developed to a pitch that was almost superhuman, and the best of their weapons was poison in infinite variety, whereof the guild alone understood the properties and preparation.

Therefore there was nothing strange, nothing unusual in this deed of devilish and cunning murder that the sight of its doing should stir him thus, and yet it did stir him.

He was minded to stop the plot, to let things take their course.
Some sense of the futility of all such strivings came home to him, and as in a glass, for Hokosa was a man of imagination, he foresaw their end.

A little success, a little failure, it scarcely mattered which, and then--that end.