Mercedes awakened in 1809, after watching her youngest son die. An old man named Senex helped her begin the last rites, and suddenly she saw an angel merged with her, its hands as bloody as her own. Her natural wisdom guided the knives that became her weapon of choice. She was a prodigy even among the Old Man's elite students, and certainly worth the risk he took in coming to Earth for her.
In march 1887, Mercedes, Senex and Alexander Gericault, covert nephandus mage, celebrate the assassination of an industrial giant. While dancing, Gericault admits to Mercedes that he's fallen in love with her.
In may 1889, while vacationing undercover as British gentry Mr. and Mrs. Melvin Abercrombie, Gericault reveals to Mercedes that he's a Nephandus. He was supposed to spy on Mercedes and Senex, discover their weaknesses, and direct them to their common enemy, the Physician and the Technocratic Union. He only remained because he fell in love with Mercedes. He says he has to leave, and asks her to join him.
In October 1896, Mercedes steps into a Caul, prepared to become a Nephandi barabbi. She does this out of love of Alexander Gericault. In December 1923, Mercedes and Alexander face off against Senex. Senex shows Mercedes how twisted her Avatar has become. She willingly hesitates the split-second he needs to kill her.