Bille is a member of The Whalers and the second-in-commandand of their leader Daud. She assists Daud in his missions and gives him information about his surroundings. However, Billie secretly teamed up with Delilah Copperspoon to defeat Daud and take over the organization but failed.
Billie Lurk was born on the 2nd day of the Month of Hearths in 1813 and grew up in Dunwall, spending her early years in the house of her alcoholic mother. She fled from home, starting an amateur career of thievery and assassination to avoid working as a mudlark or child prostitute. She hoped to one day leave such work behind to become a ship captain. One of her targets was, unbeknownst to her, the son of the Duke of Serkonos. Lurk was now a wanted fugitive, unable to find shelter or refuge anywhere. One night, Billie witnessed Daud complete a triple-assassination and was so fascinated by his skill that she decided to follow him. Daud, aware of her presence, allowed Billie to trail him to his base of operations before confronting her. Impressed by her skill and courage in the face of likely demise, Daud spared Billie's life and offered her the opportunity to train with him.
Billie eventually rose to Daud's second-in-commandant, believing that both of them knew that at one point she would be the one to take over the organization from Daud.
During The Knife of Dunwall, Billie accompanies Daud on all his missions, providing him with information about the surroundings and oppurtunities. She informs Daud about the interrogation room and the shipping crate in Rothwild Slaughterhouse, providing the room for Daud to torture Bundry Rothwild. While fleeing the compound she is caught by three Overseers and Daud has to rescue her before the two of them leave the area.
During Daud's attack on Barrister Timsh Lurk reveals to Daud that they had intended an attack on Timsh anyhow as Timsh had many enemies. During the misison, Lurk waits on a roof on the building next to Timsh's mansion. Should Daud visit the Outsider Shrine in the area Lurk appears next to him, stating that she always wondered how the Outsider smells and whether he asks questions.
After Daud returns from Timsh's mansion, he finds out that Overseers led by Overseer Hume have attacked the headquarters. In low chaos, Lurk is the one to warn Daud about the Overseers, in high chaos she is absent and a random assassin takes her place. Daud is forced to free the captured assassins and take down Hume. After this is done, Daud and his remaining assassins meet up in front of the headquarters. There, Lurk arrives, dependent on the chaos level either claiming that she was occupied fighting Overseers elsewhere or confessing that she was the one to reveal the location of Daud’s hideout to the Overseers, planning to murder Daud in the chaos to take his place. She now either starts a duel with Daud witch determines the leadership of the Whalers, or surrenders herself to Daud to decide her fate. In both cases Daud can either spare her, causing her to flee Dunwall on a boat, or kill her.
- If Lurk is spared, Daud can find a letter of her at the beginning of The Brigmore Witches.
- Despite working with Delilah to accomplish their mutual goals, Billie does not appear to respect her - when the two meet at the end of The Surge, Billie either argues with Delilah (low chaos), or commands her to be silent (high chaos)
- Billie's Windblast-like scream and her ability to shoot shadowy darts from her wrist are powers commonly used by the Brigmore Witches