Why was Stinky the goblin glowing blue?

I was listening to it on audiobook, so maybe I missed something, but all I remember is Stinky glowing blue, Vimes muttering "St. Unguluant's Fire!" and then that's about it.




Also, I liked Snuff... but it's definitely odd to see how he's essentially Superman, now. Not only does he have all of his normal Determinator policeman powers, but he also has his Darkness powers, AND basically every ruler on the Disc thinks highly of him. Where can he go from here?