Ursa, Queen of Clubs

+1: Tap one of your lands. If its a swamp all non-black creatures get a -1/-1 counter. If its an island all non-blue creatures become tapped.
-4: All enemy creatures get two -1/-1 counters. If any creatures are killed this way, add an additional -1/-1 counter to survivors. Repeat.
-6: Sacrifice a creature. The sum of that creatures power and toughness become -1/-1 counters that you can place on any number of enemy creatures.