Urza, Lord High Artificer

When Urza, Lord High Artificer enters the battlefield, create a 0/0 colorless Construct
artifact creature token with "This creature gets
+1/+1 for each artifact you control."
{t} an untapped artifact you control: Add {u}.
{5}: Shuffle your library, then exile the top card.
Until end of turn, you may play that card without paying its mana cost.