At the beginning of each player's upkeep, that player chooses artifact, creature, land, or non-Aura enchantment. All nontoken permanents of that type phase out. (While they're phased out, they're treated as though they don't exist. Each one phases in before its controller untaps during their next untap step.)
Mana cost
1
U
U
Mana value
3
Printings
From
$2.36
EDHREC rank
#23174
Reserved list
Never reprinted
Buy
Formats
Legacy
Legal
Vintage
Legal
Commander
Legal
Rulings
4 Oct 2004
Does not affect token permanents, only cards.
1 Aug 2005
Can affect itself if you choose "non-Aura enchantment".
1 Oct 2008
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.