Altar of Bone | Magic: The Gathering
Formats Altar of Bone is Legal in
Official Oracle Text for Altar of Bone
Search your library for a creature card, reveal that card, and put it into your hand. Then shuffle your library.
Official Rulings for Altar of Bone
4/1/2008 : A "creature card" is any card with the type Creature, even if it has other types such as Artifact, Enchantment, or Land. Older cards of type Summon are also Creature cards.
4/15/2013 : You must sacrifice exactly one creature to cast this spell; you cannot cast it without sacrificing a creature, and you cannot sacrifice additional creatures.
4/15/2013 : Players can only respond once this spell has been cast and all its costs have been paid. No one can try to destroy the creature you sacrificed to prevent you from casting this spell.