Concordant Crossroads

• WWizards of the Coast2008-10-01
  Official Ruling
  This has the supertype world. When a world permanent enters, 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 at the same time, they're both put into their owners' graveyards.
• WWizards of the Coast2009-10-01
  Official Ruling
  This ability affects all creatures, not just the ones you control.

Rulings via Scryfall