In the Eye of Chaos
{2}{U}
World Enchantment
Oracle Text
Whenever a player casts an instant spell, counter it unless that player pays {X}, where X is its mana value.
Watch Out
Cast trigger fires even if counteredWatch Out
This triggers when the spell is cast, before it resolves. Even if the spell is countered, the cast trigger still resolves. Copies of spells are not cast, so they won't trigger this.