Centaur Ruins enters the battlefield tapped unless you control two or more creatures.
: Add to your mana pool. Return Centaur Ruins to its owner's hand.
, Sacrifice Centaur Ruins: Add to your mana pool.
: Add 
to your mana pool. Return Centaur Ruins to its owner's hand., Sacrifice Centaur Ruins: Add 
to your mana pool.
