Come One, Come All

As an additional cost to cast Come One, Come
All, reveal a creature card from your hand.
You may cast the card revealed this way
without paying it's mana cost. If an opponent
is able to counter this spell, that spell costs {1} less to cast.
"Welcome! Welcome! Welcome to my show! Behind
this curtain is a wide variety of creatures from all
around the world. All for the low low price of $10,000!
It's a steal!"
-Barnes, King of the Goons