The Darci doll was a successful doll franchise. Lana Lang even had the whole collection of it when she was a kid. Toyman created Darci years later based on the Darci doll line up so he could have a mate. He unfortunately gave her too much free will and Darci decided to leave Toyman when she realized he was only interested in playing with toys.
Darci left Toyman and became a fashion model working for Lana Lang. She later became Lana's star model overtime, attracting Toyman's attention. He sent three toy robots to kidnap Darci during a fashion show. Superman destroyed the robots and saved Darci when he was interviewing the show as Clark Kent. Darci refused to give any information to the police after the rescue. Both Superman and Lana suspect the model knows more than she is letting on. Toyman figured out the hotel Darci was staying at and refuses to give up on her. He sent a toy kangaroo to capture her but Superman destroyed it but Darci's face and skin were damaged. She tries to repair it that night but Lana found her. Darci told Lana of her origins and that she is going to kill Toyman to stop him. Darci caused a fire in the building when Lana tries to stop her. Darci continued her search for Toyman and left Lana for dead to perish in the flames. Superman fortunately arrived and saved Lana.
Darci confronts Toyman at his hideout and prepares to kill him. She later found out that she couldn't because Toyman implanted a fail-save device in her that makes her not able to harm Toyman. Darci told him she would never love him, but Toyman responded that he knows there is a special place for him in her "heart" and said he just had to find it, and approached her with a drill. Toyman took Darci and placed her in a container based on the Darci dolls line up. Superman entered Toyman's hideout and fights against him for Darci's freedom. Toyman traps Superman in an energy cage and leaves with Darci. Darci realized that she can't harm him but she can harm his toys so she destroys Toyman's helicopter, sending both of them to the ocean. Darci was later boarding a train out of Metropolis, leaving the city for good.
At some point, Darci takes on the identity of Ms. Moore and becomes a teacher at Dakota Union High School. As a teacher, she befriends Daisy Watkins and plans to take her identity. Toyman survived the fall and sent his toys to ambush Darci both on a school bus and in school. Superman arrived in Dakota to watch Darci and stop Toyman's attacks. On his second attempt, his clown toys captured Daisy while fighting both Superman and Static. Both of the superheroes realized that Daisy was Toyman's target, not Darci. At Toyman's hideout, Darci revealed that she worked with Toyman all along so she could have a new body for herself. She used her position to study Daisy closely so she could completely take her identity. Toyman used a machine that sculptured the nanites into a copy of Daisy's body and transfered Darci's mind into it.
When Toyman captured Superman and Static, Darci betrayed him and told Toyman that she only needed him for a new body. But before Darci could kill Toyman, she noticed Daisy escaping and goes after her. Darci tries to kill Daisy by throwing her into a vat of molten plastic. When Static arrived, Darci switches positions with Daisy to fool the superhero into thinking that she is the real Daisy. Both Daisy and Darci claimed to be the real Daisy. Superman examined both of them with his X-ray vision but find them to be an identical match.
Static makes an electrical aura that surrounds all living beings and finds that the fake Daisy does not have one. Darci tries to get rid of the heroes and Toyman with an explosive ping pong ball but she falls down to the ground and begins to melt. Toyman revealed to Darci that he encoded an fail-safe device that would kill her should she betray him, knowing that she would betray him sooner or later. He tells her that he has the antidote but he throws it into the molten plastic after Darci tries to manipulate Toyman into giving it to him. After Toyman tells that she "doesn't play fair", Darci melts into a liquid puddle and Toyman is arrested by the police, having killed his own creation.