Crafting the plague had been easy as snapping his fingers, and mayhaps that was the most distressing part of it.

...

The Grey Pilgrim could have birthed diseases and disasters that would raise the hair on the Warlock’s neck, if he so wished. But power had to used responsibly, turned to moral purpose, else it could only ever be a form of tyranny. And so Tariq had wept, and asked for the guidance of the Ophanim to create a disease that would undo the Black Knight and all his murderous designs. It was not so far removed from healing, to make someone’s body turn on itself. To allow it to spread had required learning deeper than his, but as always the Choir had provided.

At a small price, a reminder of what he wrought. He would feel the agony of all taken by the disease.

He’d come to Saudant a stranger on a dark night, and seeded this foul miracle in a single man before taking his leave. Ten days and ten nights it would wait, before beginning to kill.

- Book 4, Interlude: Queen's Gambit, Declined