I had an interesting interaction at a Legacy tournament yesterday I wanted to bring up as a sanity check on the open boards. I've already solicited one opinion which says I made the right call but I am still thinking about the situation and wondering what would have happened if the opponent hadn't agreed in the following scenario:

AP taps out with City of Traitors, Plains, and Cavern of Souls (named: Eldrazi) and says, “Tap for Eldrazi mana” then casts Thought-Knot Seer.

NAP asks, “That's non-land only, right?” and after AP answers affirmatively, they return an Underground Sea to their hand as the alternative casting cost for Daze.

AP says, “Daze resolves and does nothing. ETB trigger?”

NAP reveals his hand to show 2 Underground Seas.

I stop the match and ask AP to tell me what just happened. He says he specifically said he was tapping Cavern for “Eldrazi mana” to indicate that the mana would make the Thought-Knot Seer uncounterable so the Daze does nothing, he doesn't need to pay 1, and the Thought-Knot enters the battlefield uncountered.

I look to NAP and ask if he agrees with that explanation. He nods yes.

I take this to mean that the players have established their own shortcut and let it stand, but I inform AP that “Eldrazi” is not a color and he needs to make a legal choice in the future.

I don't like the call because when OGW first came out the new colorless symbol was often referred to as “Eldrazi Mana.” In my circles tapping for “Eldrazi Mana” (ie: a pain land) means colorless.

There were multiple reasons why I let it stand, mostly that NAP agreed with AP that the Daze did nothing and by revealing his hand he has agreed with AP's suggestion of a possible outcome interpretation of events.

If NAP didn't agree with AP's recounting of events, or if he had shown any doubt about how the situation played out I would have had to say the Thought-Knot Seer was countered. Should I even have bothered to stop the match? Or am I over-thinking this seemingly simple player interaction?

Opinions?

Edited Russell Deutsch (Sept. 25, 2016 10:35:28 PM)

Personally I think you are over-thinking. Nothing in that interaction implied to me that they were tapping the Cavern of Souls for anything but the coloured mana option, and given the card they were casting doesn't require any specific colour, which colour they choose to generate is irelevant. They have a colourless source, so there isn't anything in the interaction that indicates there is any problem.

Well, which did you think was more likely: Eldrazi Mana being the 1 printed on Cavern, or some unnamed color that is inconsequential because TKS doesn't have Converge or Sunburst? I'd definitely have interpreted it like the players did, that he was using the Can't Counter ability on Cavern (in accordance with the policy guideline assuming that the uncounterability is used if possible). Saying "Eldrazi Mana“ isn't anywhere near clear enough to me that he's electing to use the first mana ability.

So, I wouldn't have stepped in given that the players seemed to agree on what happened. I may have wanted to chat with NAP after the match to make sure he understands how those sort of things happen and where he went ”wrong", but it's also definitely possible that he just wanted Daze in his GY instead of exiled.

If I hear “Eldrazi mana” from a player, I am definitely going to interpret that as meaning colorless mana without any other context. If I know that it'a coming from a Cavern of Souls with “Eldrazi” as the chosen creature type, then I'm going to ask the players to clarify since it could mean either.

In this case, since the resulting sequence of game actions was legal, I see no reason to step in here even if NAP had claimed that he thought the Thought-Knot Seer were counterable. While AP was definitely unclear, NAP compounded the error by not clarifying what had happened before casting Daze. It's clear to me what AP meant to do, even if he didn't articulate it correctly, so I'm going to say that's what happened.

Historically, we have taken tapping a Cavern of Souls to cast a creature spell of the named type as using the coloured mana to make said spell uncounterable.

The only time I'd step in here, I think, is if Cavern of Souls was the only colourless source for the spell, and at the point which Daze does not counter it, there is some confusion as to what is occurring.

“Eldrazi Mana” for me is synonymous with “Wizard Mana” or “Badger Mana”, depending on what creature type is named for Cavern of Souls – It just meshes poorly with the local colloquialisms you've experienced for colourless mana.

In the Colorado region of the United States, I have never heard colorless
mana referred to as “Eldrazi mana”. It was news to me that such a phrase
could be interpreted to mean “colorless mana.”

There is no need, to my mind, to be pedantic about requiring a legal color
choice for Cavern in this situation. The casting of the spell is legal,
and we certainly don't require a color choice to be made when tapping other
lands that produce multiple colors when it's not relevant. If NAP had
tapped both Underground Seas to cast Daze, we would not have intervened and
told her she had to make a legal choice for what color mana was produced to
cover the 1 generic mana in Daze's mana cost. AP is actually doing a bit
more than he is required to do by clarifying which of Cavern of Souls' mana
abilities he is using, since as Jack noted, we have a long-standing
shorthand to use with Cavern that covers AP in this situation.

I would step in when Daze was cast and resolved and ask what was named for
Cavern of Souls. When AP tells me “Eldrazi,” provided there was a
colorless source for Thought-Knot Seer, I would nod and move on.

I'd ask what they meant by “Eldazi Mana”

If they said colourless I would say the first ability was used

If they said something along the lines of “the mana that makes Eldrazi unable to be countered” I would say the second was used for an unspecified colour.

I think it's pretty easy to see your point on how it can be viewed as ambiguous, the thought here isn't that they aren't saying things 100% correctly up to rules standards, it's more about helping AP avoid getting burned in the future.

What it comes down to though, even if NAP DID contest that ‘eldrazi mana’ meant colorless, what would be our next course of action? Likely to ask some questions, and conclude that, while NAP might think ‘eldrazi mana’ means colorless in this case, AP didn't mean that, and It'd be hard to pitch a wording to me where I don't think eldrazi mana means ‘mana of any color for eldrazi creature spells’ rather than ‘colorless’, since eldrazi mana isn't a thing, “but mana usable only for a creature spell of the chosen type,” is.

Hey though, the better we educate players, the more they can avoid awkward situations where they say things in a way their opponent can interpret to their detriment. :)

In cases of communication, the most likely outcome is “we aren't called at all” because players generally communicate well enough to get by.

If I were called in this situation, it would be a simple cast of “What mana was Cavern of Souls tapped for?” – in the event of an answer like “blue” or “doesn't matter, uncounterable mana?” then no harm, no foul. In the event of an answer of “Eldrazi mana” clarify whether that means “colourless mana” or “mana to cast an Eldrazi spell”.

Approaching communication issues is an exercise in customer service, getting players on the same page, and making sure that they are communicating appropriately – colloquialisms often help (bounce your guy; flicker my creature; mill you for 3) but sometimes we just need to get everyone speaking the same language.

Jack