Rulings

• 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.2008-10-01
• If a permanent enters as a copy of another permanent, the permanent it is copying is destroyed and the copy stays on the battlefield.2004-10-04
• Since phasing in does not cause enters abilities to trigger, it is possible to phase in a card which is already on the battlefield and not trigger this effect.2004-10-04