Rhystic Cave

Oracle Text

T: Choose a color. Add one mana of that color unless any player pays 1. Activate this ability only any time you could cast an instant.

Card Rulings

10/4/2004 If a player pays , Rhystic Cave does not produce any mana, and is not considered to have been tapped for mana. Things which trigger of the land being tapped for mana will not trigger.
10/4/2004 Each player (starting with the current player and going in turn order) gets the option to pay when this ability resolves.
10/4/2004 The card’s ability has errata so you can’t activate the ability during casting of a spell or activating of an ability. This prevents you from getting into a position where someone paying could stop you from having enough mana to pay for the spell. If you want to use it pay for a spell or ability, you need to use this card before you start the casting or activating.