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."
Tap an untapped artifact you control:
Add {u}.
{5}: Shuffle your library, then exile the top card.
Until your next turn, you may play that card
without paying its mana cost.