Monica is a saintly woman who is the topic of Clifford's sermon. Saint Monica's Church is named after her. According to Clifford, she was born miraculously to ghouls. Sold into slavery, she had a difficult life but remained pious, eventually managing to show her wayward son the error of her ways.
Father Clifford tells the story of Saint Monica as follows:
All of the details regarding Monica come from Clifford's sermon. The Lone Wanderer has no way of verifying if this story is true, embellished or a complete fabrication.
Monica was a woman reportedly born to ghouls in the Great Lanta. She exhibited none of the ghoul condition, so many attributed her birth to be an act of God. She gave birth to a son much later in life, named Ehren. Monica was sold into slavery and sexually abused. She had a son, but was separated from him by the slavers. Despite this, she remained pious, and preached to her captors. Eventually she converted one of them and he helped her to escape.
Monica searched for and found her son - but found he had become a slaver himself. He took his mother as a slave, blaming her for the childhood he had lost to the slavers and severely mistreating her. Yet, regardless of her treatment, she would simply smile and say "I forgive you." This ate away at Ehren, until one day when he realized the errors of his ways and freed all of the slaves he owned.
Saint Monica appears to have several strong similarities to the real Saint Monica. While not a child of ghouls, Saint Monica was a mother of a wild and sinful son, who she continued to attempt to convert to Christianity. Her son would later become Saint Augustine. She is the patron saint of surviving abusive marriages, disappointing children, victims of abuse and converting relatives.
Monica is only mentioned in Fallout 3.