Will, The Sharp Boy

Nuh uh — {t}: Sacrifice target creature you
control, counter target spell with mana value X
or lower where X is the converted mana cost of
the sacrificed creature.
I've got a power for that — Sacrifice Will, The
Sharp Boy. Search your library for any card with
mana value X or lower where X is the power of
Will, The Sharp Boy. Cast that card without
paying its mana cost.