Name:Cavern of Souls
ManaCost:no cost
Types:Land
K:ETBReplacement:Other:ChooseCT
SVar:ChooseCT:DB$ ChooseType | Defined$ You | Type$ Creature | SpellDescription$ As CARDNAME enters the battlefield, choose a creature type. | AILogic$ MostProminentInComputerDeck
A:AB$ Mana | Cost$ T | Produced$ C | SpellDescription$ Add {C} to your mana pool.
A:AB$ Mana | Cost$ T | Produced$ Any | RestrictValid$ Creature.ChosenType | AddsNoCounter$ True | SpellDescription$ Add one mana of any color to your mana pool. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.
SVar:Picture:http://www.wizards.com/global/images/magic/general/cavern_of_souls.jpg
Oracle:As Cavern of Souls enters the battlefield, choose a creature type.\n{T}: Add {C} to your mana pool.\n{T}: Add one mana of any color to your mana pool. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.