Summon Harpies

As an additional cost to cast this spell exile any
number of creature cards in your graveyard with combined toughness of X. Create X 1/1 Black
Harpy creature tokens with Flying. X cannot be greater than your devotion to black.
What do you call a flock of harpies? Why a murder of course. A murder of harpies seems remarkably apt.
~ Noe-Kan, Overlord of the Abhorrent