The mana value of the back face of a nonmodal double-faced permanent or spell’s back face is calculated as though it had the mana cost of its front face. If a permanent or spell is a copy of the back face of a nonmodal double-faced object (even if the card representing that copy is itself a double-faced card), the mana value of the copy is 0.
September 24, 2021 · Innistrad: Midnight Hunt
The mana value of a transforming double-faced permanent or spell’s back face is calculated as though it had the mana cost of its front face. If a permanent or spell is a copy of the back face of a transforming double-faced card (even if the card representing that copy is itself a double-faced card), the mana value of the copy is 0.
April 22, 2021 · Strixhaven
The mana value of a transforming double-faced permanent’s back face is calculated as though it had the mana cost of its front face. If a permanent is a copy of the back face of a transforming double-faced card (even if the card representing that copy is itself a double-faced card), the mana value of that permanent is 0.
September 25, 2020 · Zendikar Rising
The converted mana cost of a transforming double-faced permanent’s back face is calculated as though it had the mana cost of its front face. If a permanent is a copy of the back face of a transforming double-faced card (even if the card representing that copy is itself a double-faced card), the converted mana cost of that permanent is 0.
May 3, 2019 · War of the Spark
The converted mana cost of a double-faced permanent’s back face is calculated as though it had the mana cost of its front face. If a permanent is a copy of the back face of a double-faced card (even if the card representing that copy is itself a double-faced card), the converted mana cost of that permanent is 0.
January 25, 2019 · Ravnica Allegiance
The converted mana cost of a double-faced permanent's back face is calculated as though it had the mana cost of its front face. If a permanent is a copy of the back face of a double-faced card (even if the card representing that copy is itself a double-faced card), the converted mana cost of that permanent is 0.
September 29, 2017 · Ixalan
The converted mana cost of a double-faced permanent’s back face is calculated as though it had the mana cost of its front face. If a permanent is a copy of the back face of a double-faced card (even if the card representing that copy is itself a double-faced card), the converted mana cost of that permanent is 0.
April 8, 2016 · Shadows over Innistrad
The converted mana cost of a double-faced permanent’s back face is calculated as though it had the mana cost of its front face. This is a change from previous rules. If a permanent is a copy of the back face of a double-faced card (even if the card representing that copy is itself a double-faced card), the converted mana cost of that permanent is 0.
September 30, 2011 · Innistrad
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.
June 17, 2011 · Commander 2011
When calculating the converted mana cost of an object with an {X} in its mana cost, X is
February 4, 2011 · Mirrodin Besieged
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.
October 1, 2010 · Scars of Mirrodin
When calculating the converted mana cost of an object with an {X} in its mana cost, X is
February 1, 2010 · Worldwake
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.