Can x-cost spells be cast while my opponent has void winnower
Asked by weisemanjohn 8 years ago
With the spoiling of the new card, void winnower
Can a spell with x in its casting cost, such as Fireball be cast with an odd number for x (even cmc in the stack)
Can Genesis Hydra be cast with an odd number for x (odd cmc on the stack)
Can Vines of Vastwood be cast with the kicker?
When does the winnower check cmc? When the spell is on the stack, or when the spell is in your hand?
Named_Tawyny says... Accepted answer #2
Winnower checks CMC as the spell is being cast. This is different from when it is put on the stack.
http://mtgsalvation.gamepedia.com/Casting_spells
First you announce a spell, and put it on the stack. This is NOT when legality is checked.
601.2a To propose the casting of a spell, a player first moves that card (or that copy of a card) from where it is to the stack. It becomes the topmost object on the stack. It has all the characteristics of the card (or the copy of a card) associated with it, and that player becomes its controller. The spell remains on the stack until its countered, it resolves, or an effect moves it elsewhere. Whether casting the proposed spell is a legal action isnt checked at this time.
The legality of the spell isn't checked until much later; just before costs are deduced and paid. In the intervening time, targets, modes, X value (and CMC) and other factors are determined.
601.2e Based on the previous announcements, the game checks to see if the proposed spell can legally be cast based on applicable timing rules (including ones based on the cards type) and other effects that may allow a spell to be cast or prohibit a spell from being cast. If the proposed spell is illegal, the game returns to the moment before the casting of that spell was proposed
So to answer your question, if - including X - the CMC of the spell is even, then it won't be allowed to be cast. If it's odd, it will.
September 10, 2015 2:29 p.m.
If you cast Fireball for an uneven amount, then you can't, you would have to cast it for one less or one more - 
adds that much cmc to the card it is on. X=5 + 
= 6 cmc, and cannot be cast.
Hydra for an even amount cant be cast, and so on. X adds to converted mana cost.
September 10, 2015 5:53 p.m.
Epochalyptik says... #4
For completeness's sake, kicker is irrelevant to Void Winnower. Additional costs, cost increases, and cost decreases don't change CMC. CMC is always derived from the value printed in the upper right corner of the card, regardless of whether that's the amount you're paying.
Epochalyptik says... #1
We'll need to wait for the release notes for an "official" ruling, but my impression is that an X spell can still be cast as long as its final CMC, counting the announced values of any variables, is odd. The spell's CMC is determined based on the announced values, not on how the card exists in your hand.
September 10, 2015 2:26 p.m.