Boska, Ace of Spades

( O can be paid by paying O , or by discarding
a black card.)
When Boska, Ace of Spades enters the battlefield,
up to X target creatures get -4/-4 until end of
turn, where X is the amount of cards discarded
to cast it.
Whenever you discard a card, target creature gets
-2/-2 until end of turn.