Suppose I have Yisan, the Wanderer Bard on the battleground with 5 verse counters.

Yisan, the Wanderer Bard

And then suppose I have something in my library with an {X} in the mana cost, like a Genesis Hydra.

Genesis Hydra

Do I get to play Genesis Hydra as though it were cast using {3}{G}{G}?

I'm aware of rule 107.3.g, which reads:

107.3g If an effect instructs a player to pay an object’s mana cost that includes {X}, the value of X is treated as 0 unless the object is a spell on the stack. In that case, the value of X is the value chosen or determined for it as the spell was cast.

It's my understanding that Yisan's ability goes onto the stack. Does Genesis Hydra also go onto the stack, allowing me to choose {X}? Or ... ?

  • 2
    107.3g is completely irrelevant here. Nothing on the two cards mentioned instructs you to pay a mana cost.
    – murgatroid99
    Apr 21, 2016 at 3:01
  • The irony of this, of course, is that I totally overlooked the rulings listed on the page I linked, which remove all doubt about the proper interpretation of ... If you’re playing a spell that has {X} in its mana cost and an effect lets you play it without paying any cost that includes {X}, the only legal choice for {X} is 0. This does not apply to effects that only reduce a cost, even if they reduce it to zero.
    – svidgen
    Apr 21, 2016 at 3:01
  • @murgatroid99 Ah. Touche.
    – svidgen
    Apr 21, 2016 at 3:02
  • That ruling is also irrelevant. You're not casting the card either. You're just putting it onto the battlefield.
    – murgatroid99
    Apr 21, 2016 at 3:02
  • 1
    @murgatroid99 Well don't I just feel silly now.
    – svidgen
    Apr 21, 2016 at 3:03

1 Answer 1


There are two relevant (overlapping) rules for this situation:

107.3f If a card in any zone other than the stack has an {X} in its mana cost, the value of {X} is treated as 0, even if the value of X is defined somewhere within its text.

202.3c When calculating the converted mana cost of an object with an {X} in its mana cost, X is treated as 0 while the object is not on the stack, and X is treated as the number chosen for it while the object is on the stack.

So, in this case, Genesis Hydra's CMC is always 2 when it is in your library, so you can only search for it if Yisan has exactly two verse counters. Then, if you do search for it and have it enter the battlefield, X is still considered to be 0, so it has no +1/+1 counters and dies immediately.

  • Does the same hold true for Genesis Hydra's ability? If I pay {5}{G}{G} for him, reveal 5 cards, and there happens to be another Genesis Hydra (or similar), does the revealed card avoid the stack and therefore force {X} to be 0?
    – svidgen
    Apr 21, 2016 at 2:57
  • It works exactly the same way for exactly the same reason. Genesis Hydra says that you put the card on the battlefield, so it goes to the battlefield, not the stack.
    – murgatroid99
    Apr 21, 2016 at 3:01

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