Some spells, such as Voodoo Queen (Water Magic), give you a chance to Curse a monster. 
When a monster is Cursed, it turns purple. A Voodoo Doll icon and turn counter appear in front of it, showing how many cards you can draw before the effect ends. While Cursed, each Voodoo Doll card you play deals extra damage to the monster.
Other spells that may also give a chance to stun a monster include:
- Water Book (Water Magic)
Tips: Water Magic is most effective on Fire Mountain. Smaller monsters like the Pufferfish or Water Jelly are more susceptible to being cursed. 
Learn more about: Challenge - Defeat X Cursed Monsters