Transfiguration Plague

Stormkicker {1}{b}{b} - (You may pay an additional {1}{b}{b} any number of times as you cast this spell.
If you do, copy it for each time you paid this cost.)
Sacrifice a creature. If you do, search your library
for a creature card with converted mana cost
equal to the converted mana cost of the sacrificed
creature, put that creature card onto the
battlefield, then shuffle your library.