Troll blood

This gray-green fluid requires, among other things, five drops of troll blood for its preparation. It becomes completely harmless if it reaches a temperature above 105 °F. The effect being very short, the poisoner usually stands in front of his victim.
A creature subjected to this poison must succeed on a DC 15 Constitution saving throw or be petrified for 1d4 round. If the saving throw fails by 5 or more, the duration is 5 rounds.