I'm curious if I'm reading this interpretation of the rules change properly.
Lets say a I control a Thespian's Stage and Omnath, Locus of Mana. I copy my opponent's Cavern of Souls with Stage. Can I then tap my Cavern for green mana using its second activated ability, despite having an undefined creature type, and then have "unspendable" green mana added to my mana pool which does not empty between phases but still gives Omnath +1/+1?
I'm reading 706.7a and 106.6: The stage doesn't enter the battlefield as a copy of Cavern and thus can't choose a creature type and has an undefined choice, while 106.6 only says the mana can't be spent, but still exists, no?
That's how I'm reading it, yeah. Cavern doesn't say you have to have a specified creature type to tap it for any color of mana, just that that colored mana can only be used to cast a creature of a specified type.
Yes, this is being clarified in the next Comp Rules update. Here's a quote from the Gatecrash rules update:
706.7a
Say you have a pair of linked abilities, and one of them asks you to choose a value or name a card, and the second one refers to that choice. This rule explains that if the first ability is copied, the choice isn't remembered and can't be used for other abilities that may copy it later. For example, if a creature becomes a copy of Voice of All (as opposed to entering the battlefield as a copy of it, in which case you can choose a color), there's no choice of color for the copy, so its protection ability doesn't do anything. Specifically, the rule said "If an ability refers to an undefined choice, that part of the ability won't do anything." But "won't do anything" was pretty vague. For example, let's say you have a Thespian's Stage that's a copy of Cavern of Souls. No choice of creature type was made for Thespian's Stage, so that part of the ability won't do anything. I imagine four reasonable interpretations of this:
The restriction of having to spend that mana on a spell of a particular creature type doesn't apply. You can spend this mana on any spell, and it can't be countered.
The whole last sentence doesn't apply. You can spend the mana on any spell. It can be countered.
The whole ability doesn't apply. You can't activate it.
The effect doesn't apply. You can activate it, but it won't produce mana.
So, we're cleaning up the rule a bit to simply say the choice of creature type for the Thespian's Stage is undefined. Also, rule 106.6 clarifies what can be done with mana that can be spent only on a restriction based on an undefined choice. (It can't be spent.)
So yes, you will be able to tap the Stage Cavern for mana via the second activated ability. The mana can't be used, but it will still be produced.
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Scientists have calculated that the chance of anything so patently absurd actually existing are millions to one. But magicians have calculated that million-to-one chances crop up nine times out of ten.
Lets say a I control a Thespian's Stage and Omnath, Locus of Mana. I copy my opponent's Cavern of Souls with Stage. Can I then tap my Cavern for green mana using its second activated ability, despite having an undefined creature type, and then have "unspendable" green mana added to my mana pool which does not empty between phases but still gives Omnath +1/+1?
I'm reading 706.7a and 106.6: The stage doesn't enter the battlefield as a copy of Cavern and thus can't choose a creature type and has an undefined choice, while 106.6 only says the mana can't be spent, but still exists, no?
This would also similarly apply to Glissa Sunseeker, right?
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So yes, you will be able to tap the Stage Cavern for mana via the second activated ability. The mana can't be used, but it will still be produced.
Scientists have calculated that the chance of anything so patently absurd actually existing are millions to one. But magicians have calculated that million-to-one chances crop up nine times out of ten.