Case of the Burning Masks
Enchantment - Case
(CMC 3)
When this Case enters the battlefield, it deals 3 damage to target creature an opponent controls.
To solve -- Three or more sources you controlled dealt damage this turn. (If unsolved, solve at the beginning of your end step.)
Solved -- Sacrifice this Case: Exile the top three cards of your library. Choose one of them. You may play that card this turn.