Spark, also known as Ash, is Chade's most recent apprentice.
Spark was born in the brothel where her mother worked as a prostitute. To prevent Spark from being forced into service at the brothel, her mother disguised her as a boy shortly after she was born. Chade encounters Spark during one of his visits to the brothel, and hires her as an errand boy. After Spark's mother is murdered by one of her clients, Spark becomes Chade's apprentice.
Spark continues presenting as her male alter ego, named Ash, in order to facilitate her duties around Buckkeep Castle. She is apt enough at disguising herself that she manages to keep the injured Fool ignorant of her dual identities as she tends to him in Fool's Quest. She is friendly with the Fool, Perseverance, and Motley the crow.
Fitz discovers that Ash is actually a girl when he witnesses her interacting with the blind Fool in Chade's room. As both Fitz and the Fool knew Ash, this comes as quite a surprise.
Ash becomes close with the Fool and agrees to help him regain his Skill fingerprints. Ash and the Fool, now presenting as Spark and Amber, respectively, travel through Skill-pillars to the Mountain site where Fitz, Perseverance, and Lant are camping. They leave their baggage and step back through the pillar to Kelsingra. When they arrive, Spark is overwhelmed by the Elderling memories. They eventually find their way to the Silver well, where Amber re-silvers her fingers. They are accosted by Rapskal and Heeby, but manage to outrun Heeby and escape through the Skill-pillar.
When they re-emerge in the Mountains, Spark is insensate from the journey. The others cover her with the butterfly cloak and try to help her recuperate. Fitz eventually realizes that the memory-stone pavilion of their campsite is affecting Spark. She begins to recover after she is moved away from the Skill-pillar.
During the journey from the Rain Wilds to Clerres, Spark becomes romantically involved with Lant. He prevents their relationship from becoming physical, stating that there are already too many bastards in his family tree.