Jodah, Archmage Eternal & Phyrexian Altar

Asked by VictorSilvertome 5 years ago

I have 3 lands, a Chromatic Lantern, a Phyrexian Altar, Jodah, Archmage Eternal on the field and a Karn Liberated in my hand. Can I cast Karn for WUBRG?

FancyTuesday says... #1

If you mean to ask if you can sacrifice Jodah, Archmage Eternal to add a 5th mana to pay the alternate casting cost enabled by Jodah, I'm afraid you cannot.

Reading the rules for casting spells one could be forgiven for believing it's a legal play. Specifically, the way 601.2f and 601.2g are written suggest it's possible, but the catch comes with 601.3.

601.2f The player determines the total cost of the spell. <...> The total cost is the mana cost or alternative cost, plus all additional costs and cost increases, and minus all cost reductions. <...> Once the total cost is determined, any effects that directly affect the total cost are applied. Then the resulting total cost becomes “locked in.” If effects would change the total cost after this time, they have no effect.

601.2g If the total cost includes a mana payment, the player then has a chance to activate mana abilities. Mana abilities must be activated before costs are paid.

601.3 A player can’t begin to cast a spell unless a rule or effect allows that player to cast it. If that player is no longer allowed to cast that spell after completing its proposal, the casting of the spell is illegal and the game returns to the moment before the casting of that spell was proposed.

Following 601.2f and 601.2g in order you can pay the alternate casting cost for the spell by sacrificing the permanent enabling the alternate casting cost. But since you were casting the spell per an effect and not a game rule, 601.3 kicks in and rewinds the game because by the time the costs have been paid for the spell to be cast the effect enabling you to cast the spell is gone.

Technically you can cast the spell, but if you do so at the expense of the effect that's allowing you to cast the spell the game rewinds to before you proposed the casting of the spell.

July 1, 2018 9:53 p.m. Edited.

Rhadamanthus says... #2

Yes, it works. The decision to apply alternative costs happens near the beginning of the process, addressed in 601.2b. The check for whether the proposed spell is still legal to cast happens in 601.2e, before the total cost is determined and paid. 601.3 and its subrules just give additional details related to that check.

July 1, 2018 11:18 p.m. Edited.

FancyTuesday says... Accepted answer #3

@Rhadamanthus:
That's what I thought going in to answer this question, and indeed how I wrote up my answer at first, but the more I poured over 601.3 the more I convinced myself that wasn't the case. I got caught up in the "...you can only cast if a rule or effect allows you to" clause and saw the effect allowing you to cast the spell (under the conditions it was being cast) disappearing by the time we got to this rule that seems to check if players can cast spells.

Upon even further scrutiny you are correct, because it defines its scope as "completing the proposal of the spell" and "the proposal" is defined as 601.2a-d. The alternate casting cost is still available at that point, so 601.3 does not intervene.

Thanks for the correction! That was quite the long winded oopsy on my part.

July 1, 2018 11:57 p.m. Edited.

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