Oracle Text

You may cast spells from your hand without paying their mana costs.

Card Rulings

7/1/2012 You must follow the normal timing restrictions of each nonland card you cast.
7/1/2012 If you cast a card “without paying its mana cost,” you can’t pay any alternative costs. You can pay additional costs such as kicker costs. If the card has mandatory additional costs, you must pay those.
7/1/2012 If the card has X in its mana cost, you must choose 0 as its value.