Reverse Cast

You may choose to not pay Reverse Cast's mana cost as long as you control a land that could tap for {u}.
Counter target spell, it's controller draws a card. If you did not pay Reverse Cast's mana cost, that spell's controller may also add mana in any combination of colors to their mana pool equal to the countered spell's converted mana cost, that mana does not empty from that player's mana pool until that player's next end step.