The Izmagnus, Guildmasters

When The Izmagnus, Guildmasters enters the
battlefield, exile up to four instants and/or
sorceries from your graveyard.
Whenever you cast an instant or sorcery from
your hand, if it has the same converted mana
cost as a card exiled by The Izmagnus, you may
cast the exiled card without paying its mana
cost. If you do, return it to exile as it resolves.