Elkin Lair
Visions — rare
World Enchantment
Elkin Lair rulings:
2008-10-01: 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.
2006-02-01: You can play the card this turn, not just during the resolution of the ability.