Not much is known about Gillian (jĭl·ē·ăn), except that her parents were both Sorreters, which obviously influenced the career path she chose. In fact, her clan had included Sorreters for generations, possibly going all the way back to the founding of Sorret in 271. Her father, Rhys, spent a great deal of time in First Village, and it is rumored that he was involved in the Black Profits, possibly even its Chief Sorreter. Of course, this is dependent upon the rumors that the gang even existed prior to 899, which is the subject of much speculation. However, Rhys was in Monab in Su'gin of 881, for the annual Pilgrimage, when he was killed. (Gillian was five years old at the time, still in Sorret with her mother.) The circumstances of Rhys's death are unclear, which further fueled the rumor mills.
It's unknown at what age precisely Gillian began her training, as she was apprenticed to her own mother, and clearly had learned a fair amount of magic by the time she entered Sorret Magic Academy in 889, at the age of 13. Just five years later, she graduated to adept status, and had become a master-adept by 899, at the age of 23. At that time, she moved to First Village, a place she had visited with her mother several times in the years since her father's death. It is believed that she joined the Black Profits at that time, though whether she became the gang's Chief Sorreter then, or sometime later, is unknown. (It is, as has already been indicated, also unknown whether the gang was just forming that year, or had been active for many years already, as per the rumors.) However, there is little doubt that she already knew some of the other members of the gang, including its current don, Dirk Noir XIX (who was 17 at the time).
In 904, when the surname law was passed, Gillian and her mother chose the name "Mancer" (măn·sûr) which is derived from an ancient language of Earth, meaning "prophecy." It is also speculated that the name alludes to "necromancy," which is akin to the term "black magic."
Gillian died in 912, shortly before the Chaos War, in a failed attempt to kill Demos Royal. It is believed she was killed by René Deadzone. She was replaced as Chief Sorreter of the Black Profits by Lem Delphi.