Simple enough: Does Thalia, Guardian of Thraben increase the converted mana cost (“CMC”) of your spells because she makes them cost more? Easy answer: No! CMC -never- changes. The sum of all the symbols in the top right corner of a card is the CMC.

The only time CMC can change is with X spells. Everywhere except the stack, X is treated as being zero. But on the stack, X is whatever you choose for it as you cast it. So in your hand, Green Sun’s Zenith has a CMC of 1. One colored symbol + 0 from the X means a total of 1. But if you were to cast Zenith with X=6, then on the stack it has a CMC of 7. You’ll have to pay 7G to cast it thanks to Thalia, but X still equals 6.

It doesn’t matter what you pay for the spell. If I cast Ponder from my hand while you control Thalia, it might cost me 1U to play, but the CMC is still 1, and it’s still a legal target for Mental Misstep.

Even if you could cast a spell without paying any mana for it, Thalia still asks you to pony up 1 extra mana to pay for it. That means if you cast Gut Shot by paying 2 life, Thalia still requires a payment of 1 on top of that, and if you reveal an instant or sorcery for Galvanoth, you still have to pay 1 to cast it.

Today’s Rules Tip written by
Trevor Nuñez, Level 1 judge from Roswell, NM