Xiahou Dun, the One-Eyed | Magic: The Gathering
Formats Xiahou Dun, the One-Eyed is Legal in
Official Oracle Text for Xiahou Dun, the One-Eyed
Sacrifice Xiahou Dun, the One-Eyed: Return target black card from your graveyard to your hand. Activate this ability only during your turn, before attackers are declared.
Official Rulings for Xiahou Dun, the One-Eyed
10/1/2009 : You can't activate Xiahou Dun's ability to return Xiahou Dun itself to your hand. You must choose a target before you sacrifice Xiahou Dun, so it's not a black card in your graveyard yet.
9/20/2013 : If a turn has multiple combat phases, the ability can only be activated before the beginning of the declare attackers step of the first combat phase in that turn.