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Whenever an opponent casts a spell, Kaervek the Merciless deals damage equal to that spell's mana value to any target.
Alternative costs, additional costs, and cost reductions don’t change a spell’s mana value. Its mana value is still based on its mana cost.
An ability that triggers when a player casts a spell resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
For spells with {X} in their mana costs, use the value chosen for X to determine the spell’s mana value.
