In the Penal Colony
The Machine or Apparatus
Symbolism, Imagery, Allegory
The machine can also be read a bunch of different ways, depending on the frame you take. In Warren's religious allegory, it's something like the Church, or organized religion, which is responsible for enforcing God's law on earth. It can be brutal and painful, but ultimately it's necessary for the "redemption" of human beings.
In a totalitarian reading of the story, the machine is more like an elaborate torture device, and that's that. On a traditional religious society reading, it could be considered an instrument for ritual sacrifice, or it could represent the elaborate set of beliefs and practices of a religion caught up in ritual sacrifice.