Oblivion Ring | Magic: The Gathering
Formats Oblivion Ring is Legal in
Official Oracle Text for Oblivion Ring
When Oblivion Ring leaves the battlefield, return the exiled card to the battlefield under its owner's control.
Official Rulings for Oblivion Ring
10/1/2007 : If there are no nonland permanents on the battlefield other than an Oblivion Ring, and the card it exiled was another Oblivion Ring, casting a third Oblivion Ring will result in an involuntary infinite loop that will end the game in a draw (unless someone chooses to break it by putting another nonland permanent onto the battlefield or destroying one of the Oblivion Rings, for example).
10/1/2008 : If the exiled card is an Aura, that card's owner chooses what it will enchant as it comes back onto the battlefield. An Aura put onto the battlefield this way doesn't target anything, but the Aura's enchant ability restricts what it can be attached to. If the Aura can't legally be attached to anything, it remains exiled forever.
7/1/2012 : Auras attached to the exiled permanent will be put into their owners' graveyards. Equipment attached to the exiled permanent will become unattached and remain on the battlefield. Any counters on the exiled permanent will cease to exist.