Forgotten Reliquary

When Forgotten Reliquary enters the battlefield, exile the top 4 cards of your library face down. Fr as long as these cards remain exiled, you may look at them. (You may do this at any time)
{3}, {t}: You may cast an artifact, with converted mana cost 3 or less, exiled with Forgotten Reliquary without paying it's mana cost.
{t}: Add {c}.