Jackie Tristan is a human who formerly possessed Fullbring powers and was a member of the organization Xcution. She is a tall, dark-skinned woman with straight, chin-length dark hair, brown eyes, and full lips. Her typical attire consists of a dark brown, low-cut long-sleeved shirt with form-fitted trousers and dark knee-length boots.

Her background is marked by a deep personal tragedy that directly shaped her powers. As a child, Jackie lived in poverty. The first present she ever received was a pair of leather boots from her father. Despite suspecting they were stolen, she accepted them with joy and treasured them, cleaning them often. This happiness was shattered when she returned home one day to find her entire family had been killed. She later learned that the murder was a consequence of her father's involvement in black market dealings. The first substance to stain her cherished boots was her own brother's blood, and this traumatic event awakened her Fullbring ability. Because her power is intrinsically linked to the memory of her family's murder, Jackie is unique among the Xcution members for openly hating her own ability.

Personality-wise, Jackie presents as a quiet and composed individual, often serving as a mediating presence among the more volatile members of Xcution. She is known to break up fights between Yukio Hans Vorarlberna and Riruka Dokugamine, and often tries to counsel Riruka, seeing through her outwardly callous demeanor to the worry beneath. Jackie is practical and disagrees with taking unnecessary risks, once refusing to continue Ichigo Kurosaki's training upon seeing his deteriorating condition. Despite her often serious exterior, she possesses a deep sense of respect and gratitude towards those who show her kindness. This is most profoundly demonstrated in her willingness to commit suicide to save a person who was kind to her, even though she barely knew him.

In the story, Jackie first appears as a background member of Xcution when Ichigo is brought into their headquarters. She expresses relief when Ichigo agrees to help them with their goals. Her primary role during the Lost Substitute Shinigami arc is as one of Ichigo's trainers. She fights him within one of Riruka's Fullbring constructs, the "Doll House," where she demonstrates her power and pushes him to reawaken his combat instincts. Later, after the Xcution members receive a portion of Ichigo's stolen Fullbring power, she battles against the Shinigami Renji Abarai inside one of Yukio's dimensional spaces.

Jackie's key relationship in the series is with Renji Abarai. During their fight, Renji refuses to attack a woman first, an act Jackie initially interprets as condescending. However, when Renji defeats her but still refuses to kill her, insisting they will find a way to escape together, his sincere chivalry moves her profoundly. In a moment of deep sacrifice, Jackie triggers a self-destruct ability to destroy the dimension, hoping to save Renji, a relative stranger who showed her genuine respect.

Her character shows notable development. She begins as a quiet operative for Xcution, seemingly at peace with the group's plan. Her deep-seated hatred for her own powers is revealed over time, rooted in her terrible past. The encounter with Renji is a catalyst for change; his actions allow her to see her power not just as a curse, but as a means to protect someone worthwhile. After surviving her suicide attack, she loses her Fullbring abilities entirely. In the aftermath, she finds and buries the body of her comrade Giriko Kutsuzawa. In a final moment of reflection with Yukio, she admits that while she always hated her ability, she now finds herself envious of Giriko, who got to die while using his. She acknowledges that their Fullbrings were the only thing truly holding the group together. She then agrees to wait for Yukio to expand his business and re-employ the surviving members of Xcution.

Regarding her abilities, Jackie is an expert hand-to-hand combatant whose fighting style focuses primarily on powerful kicks. This method allows her to quickly dirty her boots, which is the key to her power. Her Fullbring is known as Dirty Boots. She activates it by rubbing her boots together. Upon activation, her boots extend up her legs, and she generates armor on her shoulders and forearms, a scarf around her neck, and a dark hat with a cloth hanging over part of her face.

The core strength of Dirty Boots is that its power increases immensely as the boots become stained with dirt, blood, or mud. The filthier the boots, the stronger her speed and kicking force become. After receiving a portion of Ichigo's power, her Fullbring evolved. In this enhanced state, she had exhaust pipes mounted on her shoulders. These pipes could secrete a copious amount of dark, sludge-like spiritual energy that covered her entire body, further amplifying her strength to devastating levels. The ultimate technique of this enhanced state was a self-destruct ability, which cost her all of her Fullbring powers after being used.