Call it the thinking mage's version of brute force.
100 6E • ENGreg Simanson
™ & © 1993—1999 Wizards of the Coast
Legal in: Modern,Tempest Block,Legacy,Vintage,Freeform,Prismatic,Tribal Wars Legacy,Singleton 100,Commander
Oracle Text (click to copy):
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7/1/2013 Alternative costs, additional costs, cost increases, and cost reductions don’t affect a spell’s converted mana cost. 7/1/2013 If the target spell has in its converted mana cost, include the value chosen for that X when determining the value of the in Spell Blast’s mana cost. For example, if you wish to counter Volcanic Geyser (a spell with mana cost ) whose X is 7, you’ll need to choose 9 for Spell Blast’s X and pay .