Wilder, Mage of Negation

For the first time each turn, whenever a spell or ability you control counters a spell, each
opponent mills five cards. (They put the top five
cards of their library into their graveyard.)
{u}{t}: Exile target instant or sorcery card from an opponent's graveyard. Copy that card. You may
cast the copy and may spend mana as though it
were mana of any color to cast the copy.