The Fang of Critias

Exile target sorcery card with converted mana
cost X from your hand with target creature
you control. That creature gains
"{x},{t}: Copy target sorcery exiled with this
creature, where X is its converted mana cost.
You may cast that copy without paying its
mana cost. This creature doesn't untap
during your next untap step."
You may only cast one The Fang of Critias
on your turn.