For example, if I have Astral Cornucopia in play along with Jhoira's Familiar, what happens? Can I cast it for X = 1 without paying any mana?

I know that there is a question here regarding to X spells with cost reducers, but the question does not cover spells with multiple Xs, which is why I am asking this.

2 Answers 2


Casting Astral Cornucopia with X=1 and Jhoira's Familiar in play will cost {2}.

The number of Xs in a casting cost doesn't matter for cost reduction effects. If you choose X=1, the mana cost of Astral Cornucopia will simply be {1}{1}{1}, or {3}, the sum of mana symbols. Jhoira's Familiar will reduce the mana cost by {1}, resulting in a total cost of {2}.

202.1a The mana cost of an object represents what a player must spend from their mana pool to cast that card. Unless an object’s mana cost includes Phyrexian mana symbols (see rule 107.4f), paying that mana cost requires matching the type of any colored or colorless mana symbols as well as paying the generic mana indicated in the cost.

601.2f The player determines the total cost of the spell. Usually this is just the mana cost. [..] The total cost is the mana cost or alternative cost (as determined in rule 601.2b), plus all additional costs and cost increases, and minus all cost reductions.[..]

  • Alright, that makes sense. I wanted to check, as I could see it going either way, and I am not well versed enough in the rule books to go searching for information.
    – The Man
    Aug 14, 2018 at 16:37

No, if X = 1, then the card costs 2 to cast.

When casting a card with X in the cost, you choose a value for X. Then, you calculate the cost of the card based on your chosen X.

601.2b [...]If the spell has a variable cost that will be paid as it’s being cast (such as an {X} in its mana cost; see rule 107.3), the player announces the value of that variable.

601.2f The player determines the total cost of the spell. Usually this is just the mana cost. Some spells have additional or alternative costs. Some effects may increase or reduce the cost to pay, or may provide other alternative costs.

All Jhoira's Familiar does here is to reduce the total cost (normally 3) by 1.

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