Null Chamber | Magic: The Gathering
Formats Null Chamber is Legal in
Official Oracle Text for Null Chamber
The named cards can't be played.
Official Rulings for Null Chamber
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.
4/15/2013 : You choose which opponent makes the choice. Null Chamber does not target that opponent.