Text (CF+errata): 5/5, Flying. ; Whenever ~this~ deals combat damage to a player, you may cast a nonland card from your hand without paying its mana cost. [Oracle 2009/07/08]
The card is played during the resolution of the triggered ability. Timing restrictions based on the card's type (such as creature or sorcery) are ignored. Other play restrictions (such as "play only before attackers are declared) are not ignored. [Conflux FAQ 2008/12/16]
Any X in the cost of the spell must be zero. [Conflux FAQ 2008/12/16]
You can't choose any alternate costs when playing a card this way. If there are any additional costs (mandatory ones or optional ones that are chosen when playing the card), you do pay those. [Conflux FAQ 2008/12/16]
