Yuumi, The Magical Cat

: As an additional cost to attack or target Yuumi, The Magical Cat, a creature controlled by her controller must have died this turn.
+3: Yuumi, The Magical Cat deals 1 damage to target creature and prevents the next X damage to Yuumi where X is the amount of mana in your mana pool.
-4: You gain X life where X is the amount of mana in your mana pool.