Nether Void {3}{B}
World Enchantment
Whenever a player casts a spell, counter it unless that player pays {3}.
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Cards that do something similar expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.
In the Eye of Chaos 88%
#21143
"Whenever a player casts an instant spell, counter it unless that player pays {X}, where X is its mana value."
Chancellor of the Annex 88%
$2.99#10150
"Whenever an opponent casts a spell, counter it unless that player pays {1}."
Cephalid Shrine 86%
$0.29#29975
"Whenever a player casts a spell, counter that spell unless that player pays {X}, where X is the number of cards in all graveyards with the same name as the spell."
Ice Cave 82%
$0.80#20895
"Whenever a player casts a spell, any other player may pay that spell's mana cost. If a player does, counter the spell."
Vexing Bauble 80%
$2.26#1316
"Whenever a player casts a spell, if no mana was spent to cast it, counter that spell."