The narrator describes the ceiling of his cell as having a panel painted with a figure of Father Time, a traditional anthropomorphized representation of the passage of time. Traditionally, he is a bearded figure who carries a scythe and some timekeeper, like a clock or an hourglass. In the story, however, there is a moving pendulum, as if symbolically marking off the time the prisoner has left. At closer inspection, the pendulum does not simply swing, it is a large razor, which will ultimately, and literally, take the life of the prisoner.
The pit, the other threatening feature of the cell, is a yawning abyss meant to symbolically represent the abyss of hell.
As the pendulum moves ever closer to the prisoner, he stops struggling and begins to think of it as a "bauble"—or toy—as if his torturers are symbolically toying with him psychologically.
The fact that the prisoner is being tortured in the context of the Inquisition might be symbolic in that it could reveal attitudes Poe had about religion. Poe scholars tend to agree that he was not a practicing Christian in most periods of his adult life, and by revisiting the horrors of the Inquisition, Poe could be reminding readers of the Church's brutality.