# MTG Graveyard casting with 'X' costs

I play a Goblin Dark-Dwellers and its ability targets a Tempt with Vengeance. From what I read I would assume it would be legal and I may cast it from the graveyard, but I may choose X to be 2 as its cast since I choose the value of X when I cast it. Or would it rather see the card when it is in the graveyard as a 0 and force me to play it out with X being 0?

My friends tell me that it would be a 0 but I insist that when it allows me to cast I may choose for it to be 0, 1 or 2 (as long as the CMC is less than 3 overall). Is this wrong of me to believe or is it correct?

• The answers are correct, but just to clarify a bit: Being in the graveyard isn't even part of the reason. The only reason X must be zero is because you are casting "without paying its mana cost". Jul 31, 2018 at 13:58
• Your comment only applies to Marcu's answer; Hackworth's only mentions the graveyard when they confirm TvG is a valid target for the Dwellers' ability. Jul 31, 2018 at 15:02
• @KamilDrakari What ikegami said, and also your comment is technically wrong - as 107.3b states, X is zero because you may cast it without paying its mana or alternative costs, and X isn't defined in the rules text. If the X of TwV was defined and would, for example, equal 2, you could cast it with the Dwellers effect and with X = 2. Jul 31, 2018 at 18:34

X will be zero

When Goblin Dark-Dwellers enters the battlefield, you may cast target instant or sorcery card with converted mana cost 3 or less from your graveyard without paying its mana cost. If that card would be put into your graveyard this turn, exile it instead.

You are casting it from your graveyard, but you don't pay its mana cost. In that case, zero must be chosen for X.

1/22/2016: If the instant or sorcery card has {X} in its mana cost, you must choose 0 as its value.

• It would be worth emphasizing, I think, that {X} has to be zero because you’re not paying its mana cost, not because you’re casting it from the graveyard. If you were casting it from the graveyard but actually paying the cost, you could choose some other {X}. (At least, IIRC.) Jul 31, 2018 at 20:14

You may cast Tempt with Vengeance with the Dwellers, but X has to be zero.

The converted mana cost (CMC) of an object is the total amount of mana in its mana cost, and X counts as zero outside the stack. When you determine the CMC of Tempt with Vengenace for the Dwellers, TwV is in the graveyard and has a CMC of 1.

202.3. The converted mana cost of an object is a number equal to the total amount of mana in its mana cost, regardless of color.

202.3d 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 when the Dwellers' ability resolves, you do get to cast TwV. You get to choose a value for X, but the X isn't defined in the rules text, so X has to be chosen as zero.

107.3b If a player is casting a spell that has an {X} in its mana cost, the value of X isn’t defined by the text of that spell, and an effect lets that player cast that spell while paying neither its mana cost nor an alternative cost that includes X, then the only legal choice for X is 0. This doesn’t apply to effects that only reduce a cost, even if they reduce it to zero. See rule 601, “Casting Spells.”

Therefore, X has to zero when you cast TwV with the Dwellers' or similar effects.