Furlok's Magnum Opus

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Exile the top X cards of your library face down. Until the end of your next turn, you may play those cards. If you cast a spell this way, pay life equal to its converted mana cost rather than pay its mana cost. If X is four or greater, target
opponent pays any life you would have paid to cast spells u