After being banished from Deltora by King Lief, the Shadow Lord took many Deltorans hostage in the Shadowlands and began working on a new way to invade the land. It also plotted ways to kill Lief, and decided that the best way was to lure Jasmine into a trap, since Lief would follow after her. Thus, it created Faith as a way to have Jasmine come to the Shadowlands.
Cavern of The Fear
When Jasmine planned to leave the palace, Faith contacted her through the crystal and told her that she was her sister, born in captivity in the Shadowlands. Faith begged Jasmine to come free her and the other slaves, for they all were to be put to death. She also told Jasmine that Lief had known about her existence for some time but kept the information from Jasmine. Her words prompted Jasmine to leave almost immediately to find a way to get to the Shadowlands, which caused Lief to follow after her, as the Shadow Lord had planned. Later, when Lief tried to take Jasmine back to Deltora, she pleaded with him and Barda to continue on, saying that the birds told her the Shadow Lord planned to kill all its hostages. 
The Isle of Illusion
During the companion's time with the Aurons, Jasmine's thoughts continued to linger on Faith, and she never told Lief or Barda that she had spoken to her.
After arriving in the Shadowlands, Jasmine sought out as much information about Faith as she could. Inside the Shadow Factory, the companions found Pi-Ban, a member of the Shadowlands Resistance, who told Jasmine that he had overheard Faith's name being mentioned as a candidate for the Conversion Project. When the companions were captured and brought to the Shadow Arena, Lief and Barda were shocked upon seeing Faith.
Before Faith could be infested by a Conversion Project worm, the Deltoran prisoners were freed by the Shadowlands Resistance and staged an uprising in the Shadow Arena, allowing Lief to play Pirran Pipe. Jasmine tried to rescue Faith, but she revealed herself to be a shade of the Shadow Lord and blew away in a cloud of red mist.
Faith resembled a younger version of Jasmine, with the same wild black hair, pointed chin, and green eyes.
Not much is known about Faith's personality, or if she was even created with one. Like many of the Shadow Lord's creations, she is well skilled in deception, as she was able to fool Jasmine into believing that she was her sister, as well as turn her against Lief without any evidence.