When the Asgardian God of Fear the Serpent had to be defeated, Loki came up with a plan to facilitate the villain's death. He used the Twilight Shadow to write into history something that in the present could represent a moment of weakness for the Serpent so Thor could defeat him in combat.
This distraction was this Leah, based on Loki's friend. Loki wrote Leah into history, as a young Asgardian child who helped the Serpent heal from his wounds when he was a kid, and took care of him.
However, Loki wrote Leah into the history without further development, and over the years that passed, she grew resentful of the trickster for that. In mordern times, Leah allied herself with Surtur to make Loki pay. She gave the Warriors Three a Starkphone with photos and videos of Loki's mischief and deeds ordered by the All-Mothers. She also convinced Gullveig, Freyja's sister, to start a war against Asgardia. She subsequently convinced Surtur to let Loki come to her so she could fulfill her revenge against him.
When Loki traveled to Muspelheim along with Thori and Ikol, Leah attacked them and revealed her nature and motives. Rather than being impressed, Loki claimed that all of his past actions were meant to be evil. In both anger and tears, Loki revealed how much he hated all of the Asgardians and that he and Leah could make them pay by joining with Surtur and help him reduce them all into ashes. However, it turned out that was one more of Loki's lies in order to steal the Twilight Shadow from Surtur. Leah complained to Surtur that Loki had lied and tricked her again, but the fire colossus had anticipated Loki's deceit and unleashed the Hel Wolf to kill the boy.
After Loki was saved by the Dísir and Garm, he traveled back in time to the point after his past-self had written Leah into history and gave her a story, personality, and freedom of choice. Back in the present, Leah sensed that Loki changed the past and summoned him to her and Surtur's presence. Surtur tried to kill Loki, but Leah saved him. Loki explained to her that he could have saved the Nine Realms first, but then he wouldn't have been able to help her and he couldn't leave her. Deeply moved, Leah thanked Loki for what he did to her and told him he did the best he could. Now out of plans, Loki and Leah were attacked by the enraged Surtur.
After being saved by Thor and the warriors from the afterlife, Loki and Leah went to Master Wilson, who had unknowingly helped Surtur unleash the fire on the Nine Realms, and convinced him to sacrifice himself and the Manchester Gods to weaken Surtur. However, Surtur's power was still too great for Thor so Loki gave him the Twilight Shadow. Still, Leah pointed out that killing the fire colossus would create a huge amount of destructive energy and Thor told them that they'll trick Odin into helping them. Thus, Leah and Loki disguised themselves as Freyja and convinced the All-Father to come and absorb Surtur's energy as soon as the demon is killed.
Later, the two children found Daimon Hellstrom injured in Leah's cave and he told them that Mephisto had gotten the Fear Crown that Loki had created, and endangered all of reality. Excusing himself, Loki left and told her that he might have be gone for a while.
On his return, Loki refused to speak to Leah no matter how much she tried, unaware that he could only speak with three people after being blackmailed by his elder self. She took him to Hel, where he asked Brün to devour him but she refused. Then, he went to Hela and told the Goddess to send Leah away since he didn't want to have anything to do with her anymore, much to the girl's shock and outrage. Loki did this to protect Leah from his elder self as soon as he took over his body. As she was sent to the ancient past, Leah screamed at Loki to tell her what happened or at least lie, claiming that she would hate him as long there was a heart in her chest. As she disappeared, Hela comforted a crying Loki telling him that Leah would grow up knowing how to deal with the likes of him, to his confusion.
When Ikol, who had stolen Kid Loki's body, was navigating the Multiverse with the Young Avengers, they encountered Leah in a distant past. Leah told them being friends with Loki wouldn't be good for them, and vaguely introduced herself. Miss America offered her to rescue her from there, but she refused. As they were leaving to return to Earth-616, Loki told his teammates he had left Leah there to save her from himself.
Powers and Abilities
- It was heavily hinted that she and Loki had romantic feelings for each other.
- Hela hinted that she is possibly this Leah, having grown up after being left by Loki in the distant past. This revelation was designed to explain how Hela could still be the daughter of Loki (as traditionally relayed in myth), when the Goddess of Hel has appeared older than he in some stories. 
- 10 appearance(s) of Leah (Loki's creation) (Earth-616)
- 2 image(s) of Leah (Loki's creation) (Earth-616)
- 3 quotation(s) by or about Leah (Loki's creation) (Earth-616)