Boas.
203.3 - The converted mana cost of an object is a number equal to the total amount of mana in its mana cost, regardless of color. Some effects ask a player to pay mana equal to an object’s converted mana cost; this cost may be paid with any combination of colored and/or colorless mana, regardless of the colors in the object’s mana cost.
Em relaçao a custos X:
203.3b - 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.
G24.1b - In triggered abilities, X is defined when the ability resolves. It may be defined by the text of the ability, by a keyword ability of the card, or by the trigger event. See Rule 410, "Handling Triggered Abilities."
Em relaçao ao Wren’s Wrun Vanquisher, o cmc dele é 2. O custo adicional nao tem nada a ver com o CMC dele.
203.4 - Any additional cost listed in an object’s rules text or imposed by an effect isn’t part of the mana cost.
Em relaçao ás tuas 2 situaçoes:
- Banefire com X=2, tem CMC 3 enquanto na stack, e Mistmeadow Skulk nao pode ser alvo de magicas de CMC 3 ou mais graças á sua protecçao.
- CMC de Vanquisher é 2, logo a protecçao do Mistmeadow nao intervem.
Cumps