Calciform Cavern enters the battlefield tapped.
: Add or to your mana pool.
Put Calciform Cavern on top of your library: Add to your mana pool.
: Calciform Cavern becomes a 2/2 black Rat Skeleton creature until end of turn. It's still a land.
: Add 
or 
to your mana pool.
to your mana pool. : Calciform Cavern becomes a 2/2 black Rat Skeleton creature until end of turn. It's still a land.
