When Lydia came to Aliren she met Tristan, a knight. Spending sometime together they became close Tristan developed feelings for her.
After the battle was won Lydia rushed into Tristan's arms, happy that he was alive. Tristan kissed Lydia for the first time. Lydia was caught off guard, she pulled away and told him she had feelings for someone else. Tristan understood, he backed off and stayed friends with her.
When Lydia became ill and she believed she was going to die she made Tristan swear that he would look after Nathaniel and protected him. Tristan swore to her. When Lydia survived Tristan was relieved, but he kept his promise he made to her.