9

Can I cast Quarantine Field with Brisela, Voice of Nightmares in play for my opponent?

I just tried, Magic Online wouldn't let me.

But with X as 2 Quarantine Field has a CMC of 6.

Is this right?

  • As far as I remember you should be able to cast it. But my knowledge of magic rules is somewhat rusty and outdated. – tsuma534 Sep 15 '16 at 12:58
9

You can cast Quarantine Field while your opponent controls Brisela, Voice of Nightmares, as long as you choose 1 or greater for X.

First, before you even begin to cast a spell, the game checks to see if you are allowed to do so. The game ignores any effects that require information determined during the spell’s proposal (this is an exception described in 601.2). This means that we ignore Brisela's effect for now.

601.2. [...] A player must be legally allowed to cast the spell to begin this process (see rule 601.3), ignoring any effect that would prohibit that spell from being cast based on information determined during that spell’s proposal. [...]

Second, we follow the steps for casting a spell as described by 601.2a through 601.2i.

  • 601.2a - Put the spell on the stack.
  • 601.2b - Choose a value for X.
  • ...
  • 601.2e - Check if the spell can legally be cast. (This time, no exception is made for effects that require information determined during the spell’s proposal.)

When we reach 601.2e, the spell is on the stack and has a value chosen for X. According to 202.3c, the converted mana cost of a spell on the stack includes X.

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.

If you choose a value of 2 for X while casting Quarantine field, then the converted mana cost will be 6. 6 is not "3 or less", and so the spell is legal.

9

The Gatherer page for Brisela has this ruling:

For spells with {X} in their mana costs, use the value chosen for X to determine if the spell’s converted mana cost is 3 or less. For example, your opponent could cast Burn from Within (a spell with mana cost {X}{R}) with X equal to 3, but not with X equal to 2.

You should have been able to cast the spell, so you should report this as a bug.

8

Yes, you can cast Quarantine Field. Rule 202.3c states:

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.

And Rule 601.2b specifies that the XX have a value as soon as you state that you want to play that spell:

[...] 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. [...]

  • Can you explain the rule that allows you to even start casting it though? As 202.3c says, x is 0 while the object is not on the stack. So while it's in your hand, it has a CMC of 2, so it seems like it's an illegal option to say "I cast this". It would only become legal once it gets to the stack. – GendoIkari Sep 15 '16 at 13:40
  • "Casting" is moving an object from any zone (usually your hand) to the stack. When you do that, you immediately specify what options you choose for that card: any "Choose one:" modes, any X in the casting cost - everything that determines the final shape of the spell and its cost. This is an atomic action: one moment you have a card with CMC 2 in your hand, the next you have a spell with CMC 6 on the stack. Brisela bars neither of those. – steenbergh Sep 15 '16 at 13:45
5

You should be able to cast it.

From the gatherer's ruling on Brisela:

For spells with {X} in their mana costs, use the value chosen for X to determine if the spell’s converted mana cost is 3 or less. For example, your opponent could cast Burn from Within (a spell with mana cost {X}{R}) with X equal to 3, but not with X equal to 2.

Meaning you can cast Quarantine Field for any cost greater than 0 as it will have a cmc of at least 4

-3

The converted mana cost you refer to applies only while the spell is on the stack. While it's in your hand, the cmc is 2, with X being zero. Thus, Brisela prevents you from even casting it.

  • 2
    Welcome to the site, and thanks for your answer! For most cases you'd be right - for example if you discard Quarantine Field using Blast of Genius, its CMC is 2. But for OP's case (can you cast the spell?) the rules explicitly have an exception: see the rulings for definitive proof, and the accepted answer for the specifics. – Benjamin Cosman Sep 15 '16 at 22:18

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