Some spells, such as Queen Medusa (Snake Magic), give you a chance to Petrify a monster. 


When a monster is Petrified, it turns to stone. A petrification counter appears above its head.


To complete the challenge that asks you to “Defeat X Petrified monsters", you must kill a monster WHILE it is still Petrified.


Note: If the monster is no longer Petrified when killed, then it WON'T count for the challenge.

Learn more about: How do I Petrify a Monster?