Some spells, such as Queen Medusa (Snake Magic), give you a chance to Petrify a monster. To cast this spell, you'll need to play 4 cards enchanted with Queen Medusa to summon her.

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

Note: If the monster is no longer Petrified when defeated, then it won’t count toward the challenge.

Learn more about: How do I Petrify a Monster?