Reinterpret

If a spell with {X} in its mana cost is countered this way, {X} is the value chosen as the spell was cast.

Wotc — April 16, 2021

This can be used to cast either face of a modal double-faced card, but only if the face you are casting has an equal or lesser mana value than the target spell.

Wotc — April 16, 2021

If you target a spell that can’t be countered, like Heated Debate, you won’t counter the spell, but you will get to cast a spell with an equal or lesser mana value.

Wotc — April 16, 2021

If you cast a spell “without paying its mana cost,” you can’t pay any alternative costs. You can, however, pay additional costs, such as kicker costs. If the card has any mandatory additional costs, you must pay those.

Wotc — April 16, 2021

If the spell you cast has {X} in its mana cost, you must choose 0 as the value of X.

Wotc — April 16, 2021