Jessica Cruz is a young Latino American woman who was forced to become the unwilling host to the Ring of Volthoom after Power Ring's death. Though technically she is not a "Power Ring" as she is not a member of the Crime Syndicate and has no association with the organization, for namesake purposes she is dubbed "Power Ring" while the ring uses her as a host. In her first appearance, Jessica is seen hiding in a storage room while her sister attempts to get her to come out.
Prior to this, Jessica and her friends were out hunting when they accidentally came across two men burying a body. The men brutally murder her friends to ensure there are no witnesses but Jessica manages to escape becoming the sole survivor of the incident, however she is left traumatized, guilt stricken and broken to the point where she developed agoraphobia mostly because she feared the men who killed her friends were looking for her.
Jessica's family always thought she was paranoid and disregarded her fears, but her sister later feels great remorse for this when they turned out to be true. The ring of Volthoom was able to locate her due to this great fear, which it feeds off. Jessica in the midst of tears tried to make it go away, but the ring did not. She pulled out a gun and shot it.
This only angered the ring. Jessica, unlike her predecessor did not willingly accept the ring, but it forced itself on her. Jessica was not in control of the ring and it began attacking some rescue workers with monstrous constructs. The Justice League went after her, looking for the ring, but when the Doom Patrol got to her first, she informs them that she attempted to remove the ring to no avail.
Being the new owner of the weapon, the Ring of Volthoom tortures Jessica with immense physical and psychological pain. It is shown that like Harold Jordan that she has visible harmful vein formations of her ring hand. Jessica cannot control the ring as long as Volthoom is able to dominate the ring through her fear; however when she overcomes her fears, she is able to quiet Volthoom and use the ring. The costume the ring makes her bear includes a headband and a single eye patch shaped like the ring's insignia rather than a full eye mask. The Ring of Volthoom explains that it is using Jessica to attract the being that destroyed Earth-Three to this Earth because he is now dying (for reasons not explained) and wants to take the planet with him.
Batman was able to de-power the ring after convincing her to be brave. Jessica is later seen with the Flash in the watchtower; though Batman had taken away the ring's influence he did not remove it from her hand; Jessica in a moment of fear causes the ring to restart and it attempts to attack her but the Flash reminds her that she has control over her fear. Her resolve returned; she successfully wins the battle of wills over Volthoom, who is put into dormancy once again but not before vowing to return. She then tells the Flash that she wants to learn how to use the ring's power to which the Flash agrees. Jessica then joins the Justice League, and is later seen rescuing some civilians who were nearly killed by an earthquake apparently using the ring to no ill effect on herself.
The Flash then asks her what her favorite flavor of Ice Cream is to which she replies pistachio. The Flash then appears with a cone in his hand surprising Jessica as she wonders how calm the Flash could remain in such a situation. Later, she is seen at the unveiling of the partnership between Wayne Enterprises and LexCorp though she becomes nervous since she does not like being in crowds which allows Volthoom to murmur to her, but this is revealed part of Batman's plan to help Jessica fully overcome her fear.
Jessica later becomes very sick and is seen in the Watchtower's infirmary. She succumbed to effects of the AMAZO virus, but is soon cured and voices that she is tired of being controlled. The Flash agrees and reveals that he has called in someone who can teach Jessica about rings and willpower. When a skeptical Jessica asks the Flash who could possible help her, Hal Jordan reveals himself and states that he has returned to Earth to teach Jessica how to stay in control. Jessica masters the ring under Hal's tutelage though she does mention that the ring "whispers awful things to her", somehow Volthoom has been severely weakened without affecting the power of the ring.
When Darkseid's daughter Grail arrives on Prime Earth, she attacks Jessica and says that the Ring of Volthoom is a tether to Earth-Three and that its evil power would serve her well. Grail then uses the ring to open a portal to Earth-Three allowing the Anti-Monitor to cross over to the Prime Earth. Jessica is quickly transported away along with the rest of the Justice League by Metron and watches as Batman takes his place on Metron's chair. Jessica later uses the ring to fight various enemies while Volthoom assisting her in order to prevent himself from being killed. Jessica helps Mister Miracle break out the Crime Syndicate in order to fight the Anti-Monitor.
The ring being in close proximity to the Sydnicate is able to draw off them to overwhelm Jessica and possess her body and mind. Cyborg attempts to shut him off again, but he attacks Cyborg and frees Grid. Jessica is now trapped within the Ring while Volthoom has taken over her body. Volthoom helps the Green Lantern Corp fight off Mobius's forces.
As part of DC Comics Rebirth, Jessica, along with Simon Baz will become Earth's newest Green Lanterns in charge of protecting the planet.
Info from Wikipedia and Wikia.