The Blackstone One is a train,which is commanded by Cedric. Usually, it's called Blackstone Railroad. You can use the train to move through areas.
When you go to one of it's doors and press the X button you will see the following commands:
- Go inside (enter the train)
- Leave (leave area,which opens the World Map.)
The Blackstone is used for many side characters in the game, such as Granny Rosa or Parn, if they do not have current homes to reside in throughout the game.