(: Add or to your mana pool.)
Tranquil Key enters the battlefield tapped unless you control one or more creatures.
: Tranquil Key becomes a 2/1 white and blue Soldier Angel creature until end of turn. It's still a land.
: Add 
or 
to your mana pool.): Tranquil Key becomes a 2/1 white and blue Soldier Angel creature until end of turn. It's still a land.
