In the Eye of Chaos 
World Enchantment
Whenever a player casts an instant spell, counter it unless that player pays 
, where X is its mana value.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL
World Enchantment
Whenever a player casts an instant spell, counter it unless that player pays , where X is its mana value.