Fake Magic Powder
The fake magic powder was thrown in Hudson's face by the Macbeth Robot.
The powder was a pink, sparkly substance. It blinded Hudson briefly and made him cough when it was thrown in his face. Other than that, it had no long term adverse effects.
It was successful as a ruse to make the other members of the Manhattan Clan believe that Hudson was frozen in stone at night, as Xanatos planned. ("The Price")