Choose a card name. Until your next turn, spells with the chosen name can't be cast and lands with the chosen name can't be played.
Draw a card.
2/1/2006 Players may cast spells while Conjurer’s Ban is on the stack. Only after all players pass priority does Conjurer’s Ban resolve, and that’s when you name a card. Once you name a card, that card can’t be played in response.
2/1/2006 You may name a land card to prevent it from being played.
2/1/2006 Conjurer’s Ban only affects cards. A copy of a card (for example, one created by Eye of the Storm isn’t a card, so it can be played.
8/1/2008 This can’t be used as a counterspell. It will have no effect on spells which were on the stack when it was cast, nor on those cast in response to it.