The Lucifuge, also known as the Lady of Milan, is the founder of the conspiracy that bears the same name.
The Lucifuge has led the Children of the Seventh Generation since the conspiracy's founding in 853, while she lived as a noblewoman in Milan. She employed occultists and genealogists from across Europe to identify and track the descendants of Satan throughout the known world. Whenever a suitable heir was found, the Lucifuge would offer them the choice to either renounce Satan and join the Vigil, or be destroyed.
The Lady of Milan remains as the central authority, commanding her agents across the world. The Lady of Milan is rumored to keep ancient, meticulous records of the many lineages of the devil, knowing when and where a potential hunter will come into his own. The Lady's apparent immortality is a mystery itself; some agents speculate whether she is a descendent of Satan as well, his consort, or the devil herself. Some high-ranking hunters of the Lucifuge are said to know the secret, but they aren't telling.
The Lucifuge has a relationship with Ambrogio Baudolino, and the two have secret meetings once a year or so.