Jill was born in the city of Lankhmar as the daughter of a saleswoman and rogue by the name of Nell, who, at that time, was just fourteen years old. Nell wasn't a native of the dark city, also known as the city of the black bones but she was on the run for the holy keepers of the darkest secret mankind had ever created.
Nell came from the wet and damp swamps of Holland, a small insignificant dot on the map on the coast of a northern sea. What exactly she was running for is not clear at this time but a pregnant woman certainly would never travel from the North to the end of the Sea of Monsters in these barbaric times if it wasn't for a very good reason. She did not run far enough however. What happened tot the mother we don't know, but the little Jill was brought back to the wet Holland before she was two years old. There she was brought by a monastery where she grew up, learned the trades necessary to stay alive as a girl on her own, as well as brewing beer. But most of the day she was locked away in a little room with books, written in a language she could not read, and her job was to make copies of these books with ink on parchment. She didn't have much freedom but one day she secretly met a woman, 14 years older than she was, who claimed to be her mother Nell. The woman could not stay long and was very nervous. Nell had the same features as Jill had and they discovered they had a lot in common. Nell had a little, shiny, metal colored tattoo or maybe it was a brand mark, on her breastbone. It wasn't much later that Nell again disappeared, leaving Jill with questions.
Then one day, years later, when Jill was at work something unforeseen happened. She started a new book and to her astonishment she could read it. So she discovered the secret that maybe was the same secret her mother was on the run for. And so Jill started to run too and it didn't took long before she was a well equipped deadly rogue, skilled in many sharp weapons and loaded with animal instincts. 
She traveled to all the major cities on or underneath the surface of the earth like Baldur’s Gate, Icewind and Neverwinter in The Forgotten Realms, to Ironforge, Booty Bay and Stormwind in The Eastern Kingdoms, to the cursed town Tristram were hell once broke loose, was recaptured and broke loose again, to the port city of Lut Gholein in the Western Kingdoms and to the jungle town Kurast in the East. She has seen, climbed and conquered the highest mountains in the Kingdom of Ehb and traveled by foot from the Great Northern Forest through the Endless Desert in The Utraean Peninsula to reach the Ascalon City in the Northlands of Tyria. She did not find her mother.
But on day in a small border town she met a traveling arms salesman who once every three years crossed the most unstable borders in order to obtain rare and very sought after items. He showed and eventually sold her a perfectly manufactured torso armor that fitted her body like a clove. The piece was obvious made from a very fine quality leather like demonhide or tightskin because it was extremely flexible in wearing but when hit upon it changed structure and hardened and became like steel. Later, when she was alone on a top room in the Green Dragon Inn, she took the armor off to clean it and to her horror she discovered a little tattoo or brand mark at the spot covering her breastbone. She had seen this mark before long ago and suddenly realized that the horror stories about slaves being kept alive by magical powers to forever grow and produce high quality armor for the feared dark armies of the world, perhaps were not just stories after all.