Let me tell you a little secret. X, if it’s not on the stack, is treated as 0. While an X spell is ON the stack, X stops being a variable and starts being a number (Note: the quality of the spell being considered an X spell doesn’t change; it’s still an X spell on the stack; that’s how cards like Frontline Medic work!). Once an X spell is on the stack, its CMC (Converted Mana Cost) can then be calculated.

In short, when Player A counters an X spell with Plasm Capture, Player A will be able to perform their own version of “Can’t touch this!” and will also be able to add whatever value X was at the time the spell was countered.

For example: If you cast Immortal Servitude with X=3, and I counter it with Plasm Capture, the mana cost of Immortal Servitude (3{W/B}{W/B}{W/B}) converts to 6, and I will add 6 mana in any combination of colors to my mana pool at the beginning of my next precombat main phase! To go a step further, if you Miracle Bonfire of the Damned and pay 4R (choosing 4 for X), the converted mana cost is still determined from the mana cost in the top right corner. Since you chose 4 for X, the mana cost in the top right is treated as {4}{4}R, and I will get 9 mana by countering it with Plasm Capture, even though you only paid 5 mana for it. Crazy, huh?

Today’s Rules Tip written by Eddie Cheung