Lydia was born of a Katagari Tsakalis and the Dream-Hunter Solin. Her mother wanted nothing to do with Solin after she found out he wasn't human. She asked him not to have any contact with their daughter, but she sent her to him when her pack was attacked and she was about to be killed. She also took Lydia's ability to speak so that she couldn't tell anyone about the incident. Solin raised her as his own daughter and they taught themselves sign language to communicate. He did not reveal his connection to her until she was grown.
Solin also hid from her the fact that she was the key to Olympus, meaning she had the power to kill all the Greek gods. He was kidnapped by Seth and held prisoner in Azmodea while Seth and Noir tortured him for her whereabouts. When she went there to rescue him, Seth sent Solin back to the human realm to retrieve the key, not knowing that he held it in the form of his new prisoner Lydia. He gave her back the power of speech but took her other powers. At first, she viewed him as her enemy, but she began to see the vulnerability underneath his fierceness. After Jaden revealed Seth's tortured past, Lydia began to understand him like no one ever had. She was also the first person in his life to show him genuine kindness. Therefore he protected her when Greek gods went to Azmodea and tortured him for her location. Lydia took him to Sanctuary for healing, then they hid out from both Noir and the Greek gods with Maahes, a member of Seth's pantheon. They were eventually tracked down and Seth realized that the only way to save her would be to make all her enemies think she was dead. He stabbed her, then cast a spell over her body to make it appear dead. Finally, he turned himself in to Noir and returned to Azmodea. Lydia didn't remember him after she first awoke, but she went back to Azmodea to rescue him as soon as she did. They stayed with Nick Gautier until Seth's powers returned and he was strong enough to protect them from anyone Noir might send after him in the future. They named their son Ambrose after Nick.