Lei was born among the Warforged, her parents were deeply involved in the development of them. Lei was the only child in the Cannith forgehold, and the artificers and magewrights had little time for her. As a result, Lei found her friends among the warforged, and she spent her days with the newly forged constructs that were still waiting to be shipped off to the front lines. Most of her values are drawn from her time with the guileless warforged: devotion, honesty, and trust. While she comes from a house known for its shrewd bargainers and ruthless profiteers, Lei has little gift for subterfuge and is often caught off-guard by the malicious and selfish behavior of others.
As she grew into a young woman, she proved to have an amazing gift for the art of the artificer, and soon she was working on the warforged herself. In 993 YK, her parents arranged for her betrothal to Hadran d'Cannith, but Lei's father insisted that she serve term in the military before her marriage. Lei was assigned to the southern command of Cyre.
Lei's role was technically strictly mercenary: caring for the warforged and maintaining her unit's magical equipment. However, she developed strong bonds with her comrades, and considers the warforged Pierce to be like a brother to her.
Lei's squad was fighting at the Fields of Ruin on the Day of Mourning. They all survived, and tried to find survivors in the ruins of Metrol. They found none, and eventually found their way to the refugee camp that would become New Cyre. Lei left along with Daine, Jode d'Jorasco and Pierce to go to Sharn, where her betrothed was supposed to be waiting for her.
Unfortunately, things didn't go to plan. The group dragged their feet, Lei didn't really want to go and get married to a man she hadn't met. When she arrived in Sharn, she was shunned by the members of her house. She had been made excoriate, on orders of Merrix d'Cannith himself, the patriarch of Cannith South. Even worse(?), her betrothed had been brutally murdered a week prior.
Lei, along with Daine, Jode d'Jorasco and Pierce ended up in High Walls, the refugee camp in Sharn. Jode put them in contact with a figure from Daine's past, Alina Lorridan Lyrris, a Zil noblewoman. Alina, taking pity on the group, gave them "honest" work. She thought one of her employees, a man named Rasial Tann, had stolen some Khyber shards that he was supposed to deliver and gone AWOL.
Several days later, they were attacked by some of the refugees, who had strange mutations. The attackers were led by Monan, who put himself and Daine into a coma when he was defeated. They got Daine to a House of Healing, but it wasn't until a Kalashtar named Lakashtai saw to him that he awoke. Lei stayed with him until he awoke, and while she did so, Jode went to investigate a lead, alone.
They found Jode dead in the sewers, alongside Rasial, 3 days later.
Lei wrote to Terfel Glas as this was ongoing. See Lei's Letters.
After a lengthy investigation into these events, the same group that murdered Jode kidnapped Lei and Daine. Thankfully, they were rescued by the party before Lei was also killed. Following the conclusion of this series of events, Lei and the others left Sharn for New Cyre. When the Mist Walkers claimed Avrahk Mbar'ost, Lei, Daine and Pierce relocated there.