The ghosts of anchoresses
The ghosts of the previous anchoresses are significant in this story, representing Sarah's personal connection to this historical practice. The ghosts also symbolize the threat lurking outside Sarah's cell, as we learn that one of the anchoresses had been attacked while isolating.
The Cell
Sarah's cell represents her disconnection from the outside world, and her desire to escape due to grief and suffering. She physically closes herself off from her suffering, but still must come into contact with the world in various ways, symbolizing the fact that there is no true way to escape.
Birds
At the beginning of the novel, Sarah tells us that growing up she longed to fly like a jongleur bird. In this novel, birds represent a sense of freedom from the world and its harsh realities, which Sarah never truly finds.
Sir Thomas
Sir Thomas represents male threat existent in Medieval England, where women were often blamed for any transgressions. Part of the reason Sarah decides to become an anchoress is to escape unwanted attention from Thomas. However, he then targets her servant girl, Anna, showing that the threat is not eradicated by Sarah escaping from the world.
The Anchoress
In the novel, Sarah's choice to become an anchoress is depicted as a rejection of traditional feminine roles. While Sarah had the option of marrying Sir Thomas and having a comfortable life, she instead decided to isolate and devote herself to God. Here, we see a rare option for women to have some agency for their lives during the Medieval era.