Bai Mengxin is a Nascent Soul elder of the North Night Palace residing on the frozen North Night Island that sits between the Great Jin and the Northern Seas. She is a cultivator of an Ice Flame of extreme cold.
Bai Mengxin met a Mid-Nascent Soul stage Han Li when he visited the North Night Palace in search for a Profound Ice Flower. Prior to meeting him in person, she was surprised to learn from her cousin that he had abilities on par with a Late-Nascent Soul cultivator. She believed that he did not possess such abilities because he originated from the Heavenly South. This disbelief fueled her desire to test the strength of Han Li's Ice Flame.
The grand elder of the North Night Palace was at the bottleneck of Deity Transformation. To break-through, Bai Mengxin participated in a ritual requiring five individuals cultivating Ice Flames of extreme cold. Secretly, she was also a part of the grand elder's plot to obtain Han Li's Heavenvoid Cauldron. To accomplish this, the ritual was held in the Spirit Void Hall.
After the grand elder failed to break through to Deity Transformation, she came into conflict with Han Li. When, Bai Mengxin used her sword technique against Han Li, she was countered by his Bamboo Cloudswarm Swords. Believing she had the upper-hand she became overconfident and her spiritual sense was ripped apart by his Spirit Stun Thorn technique. In her brief moment of agony, her connection weakened with her Ice Swords treasure, the swords weakened and half were destroyed by his Bamboo Cloudswarm Swords. Along with the other elders of the North Night Palace, she realized that she had underestimated Han Li's abilities and formed a new plan to jointly deal with him. However, she continued to be overwhelmed when his Golden Beetles effortlessly consumed her Twin-Tailed Human Face Scorpion.
Bai Mengxin was horrified when he captured the grand elder's Nascent Soul. She immediately attempted to flee detonating several ancient treasures in her possession to break restrictions created by Han Li. Acting on orders, Han Li's Nascent Soul-grade puppet destroyed her body by punching a hole through her abdomen. She discarded her body, attempted to flee as her Nascent Soul. However her Nascent Soul was destroyed by a followup attack by the puppet.