Cavern of Souls is seeing a lot of attention lately, especially with a question that popped up a few weeks back, as well as the reversal of the ruling that was given. The question was what the ‘standard’ is for Cavern. If you tap it without saying which of the two mana abilities you’re using, which is the default? It’s tricky, because other cards similar to Cavern have existed, but it’s always clear which you’ve used [if you tap Grove of the Burnwillows, it’ll have an immediate effect on the game state by changing life totals. Ditto for Sulfurous Springs]. With Cavern, it’s not clear. Without a ‘default’, you’d have to ask your opponent which he did, basically giving away that you have a counter and want to know if you can use it, which rewards your opponent for being ambiguous.
With that in mind, the higher-ups in the Judging world discussed it, and ORIGINALLY declared that the default was the colorless; you had to declare otherwise. That is no longer the case, thanks to a recent reversal. Right now, the [O]fficial ruling on it is that if you tap a Cavern to pay for a creature spell that matches the type named for that Cavern, that you’re producing colored (uncounterable) mana unless you say otherwise. So, if you tap a Cavern set to “Giant”, 3 Forests, and 2 Islands to cast a Primeval Titan, that Titan is uncounterable unless you say that you’re using colorless mana with your Cavern. Because of this, it’s very important that both players know exactly what creature type Cavern is naming at all times.
Today’s Tournament Tip written by
Trevor Nuñez, Level 1 judge from Roswell, NM