One obvious theme is the inexorable passage of time, ending in death as the final outcome of all life. The pendulum, usually associated with clocks and time, here combines the two elements, for it is one of two possible means of execution, and it is also compared to the scythe wielded by Father Time. The other obvious symbol of death is the pit, a synonym with death or Sheol since biblical times.
The horrors of the Spanish Inquisition are also treated specifically. This is not, however, a diatribe against Spain or a laudatory statement about France. Instead, on a more universal level, it shows the cruelty that humans exercise on their fellow human beings. Edgar Allan Poe uses the historical background solely to render the story more believable and, thus, more frightening. His purpose is to create a nightmare in which the reader becomes a coparticipant with the protagonist, sharing in the terror and the suspense.