Christy Jenkins's History
Christy Jenkins was the firstborn daughter of Carl and Helen Jenkins and the older sister of Billie Jenkins. Both Christy and her sister were latent witches who inherited their magic from their maternal grandmother, and manifested their powers only in adolescence.
Despite seemingly starting off as an innocent and later protegee of the Charmed Ones, Christy was eventually revealed to be on the side of the Triad, blinded by their lies. She manipulated Billie into turning against the Charmed Ones, culminating in a battle where she was killed when refusing to give up her misguided fight.
Early life:
Christy was born in 1984 to Carl and Helen Jenkins, and her maternal grandmother was a witch. A few years later, she became the older sister to Billie in 1986. Billie and Christy had a typical sisterly relationship, as they fought like "cats and dogs". Christy loved to get Billie in trouble and was very sneaky about it, as it took Carl and Helen a while to figure it out. Christy was described by Helen as "adoring Billie, and no one could pick on Billie, except for Christy". Christy was revealed to have been "hearing voices", indicating that her telepathy had kicked in before she was abducted.
Captivity:
When she was seven years old, Christy was kidnapped by a demon named Reinhardt and placed under the supervision of Scather Demons. The Scathers kept Christy safe in the Underworld in preparation for the return of the Triad, a trio of powerful upper-level demons.
The Triad masterminded Christy's kidnapping because they knew that she and her younger sister would eventually grow up to be extremely powerful witches, and believed that they were the key to the "Ultimate Power". They believed that if they were able to harness the sisters' power, it would be enough to tip the scales from good to evil. Over her years in captivity, they brainwashed Christy, and trained her to believe that evil was good and vice versa, with the help of Dumain, a demon who had been Christy's imaginary friend. They hoped that Christy and Billie would be able to stand against the forthcoming Charmed Ones. Eventually, they planned for the two sets of sister witches to kill each other, drastically tipping the scales in the favor of evil.
After Her Rescue:
After an encounter with a demon that brought back suppressed memories about her sister's kidnapping, Billie began searching for Christy in 2006. After mastering her Projection power, Billie found Christy in the Underworld. With the help of the Charmed Ones, Billie began teaching Christy how to reintegrate and to control her powers. At one point, Christy was kidnapped again by the same Scather demons sent by the Triad, though Billie went back to save her. While they were in the Underworld, Billie convinced Christy to break free. Together, with Christy's pyrokinetic powers and Billie's telekinetic powers, they then vanquished the demons.
Working with the Triad:
Unknown to Billie and the Charmed Ones, Christy was working together with the Triad. After years of failed attempts to kill the sisters by the Triad and the Source of All Evil, Dumain convinced the Triad to release Christy, with the goal of turning Billie against the Charmed Ones. He believed that if Christy succeeded in convincing Billie that the Charmed Ones were evil, their magic combined with the Triad's would be more than the Charmed Ones could handle. He also believed both sets of sisters would die in the ensuing battle, allowing the Triad to return. The Triad agreed with his plans and promised to make Dumain one of them should it succeed.
While the Charmed Ones originally believed that the Triad were the major threat they were supposed to face, they learned this was not the case when Leo was not returned by the Angel of Destiny after two of them were vanquished. Candor, the last member of the Triad, reminded Christy that Billie was the "Ultimate Power" and she had to "save" her from the Charmed Ones. When Candor suspected that Christy was wavering after reuniting with Carl and Helen, he sent Noxon Demons to kill her parents. When Christy disocvered this, she angrily killed him. Before Candor died, he told Christy that she had passed her "final test."
Christy later saws an opening to turn Billie against the Charmed Ones when it seemed that they were more concerned with finding Leo than tracking down the Noxons. With Dumain's help, she convinced Billie that the Charmed Ones were selfish and that they needed to be stopped before their powers corrupted them and their progeny. To help her see this, Christy and Billie used a crystal to put the sisters to sleep, allowing Billie to enter their minds and see their inner desires.
The Ultimate Power:
Billie and Christy faced the Charmed Ones in the manor with both sides empowered by the Hollow. It took "Charmed power" to summon the Hollow, so Billie and Christy used Wyatt Halliwell to summon it as well. The sisters then took Wyatt's powers. As a result, both sets of sisters were evenly matched when they faced each other. The power between them shot out in all directions, blowing up the manor and killing Phoebe, Paige and Christy, leaving Billie and Piper as the only survivors. After the battle, the Hollow returned to its containment.
Following this destruction, the Angel of Destiny brought back Leo, who stopped Piper from killing Billie. After leaving the destroyed manor, Billie returned to Magic School with Dumain. He suggested that she project herself into the past so they could get the Hollow before the Charmed Ones did. When Dumain tried to get her to focus on the Triad rather than her sister, Billie realized that she and Christy had been tricked and returned to the side of the Charmed Ones.
Leo and Piper went back in time to fix what happened, and with the help of Piper's grandmother Penny and mother Patty recreated the Power of Three to send away the Hollow just as the battle started. Billie, who also traveled back in time, told Christy that they were being used, and tried to persuade her to reverse their course. Christy refused and went back to Magic School, even after Billie told her Dumain tried to get her to go to the Triad first. A disillusioned Billie then realized her sister had turned into a killer, and that Christy was manipulating her as well.
Dumain stole Coop's ring, and he and Christy used it to travel back in time to warn the Triad about the possibility of the Charmed Ones getting the Hollow. Just as they arrived, Billie and the Charmed Ones arrived using Billie's projection power, and vanquished the Triad and both past and present Dumain. Billie tried one last time to convince Christy to reject her vendetta. In an act of rage, Christy launched a huge fireball at Billie and the Charmed Ones. Billie telekinetically deflected it back at Christy in self-defense, killing her. Billie immediately broke down in tears, as she was forced to kill her own sister.