Nether Void

Enchant World    (CMC:4)

Whenever a player casts a spell, counter it unless that player pays .

These days, some wizards are finding that they have a little too much spell left at the end of their mana.

73 ME3 • ENHarold McNeill

™ & © 1993—2009 Wizards of the Coast

Legal in: Legacy,Vintage,Commander

Oracle Text (click to copy):

10/4/2004
This is not an additional cost, it is a triggered ability.
10/1/2008
This has the supertype world. When a world permanent enters the battlefield, any world permanents that were already on the battlefield are put into their owners' graveyards. This is a state-based action called the "world rule." The new world permanent stays on the battlefield. If two world permanents enter the battlefield at the same time, they're both put into their owners' graveyards.
10/1/2009
The ability triggers whenever any player (including you) casts a spell of any type.