- “Little Treasure I managed… to get your statue back….. I should stay to protect you, but I don’t think I can…. Master, I… I love you.„
Yan'er is one of the characters in I Shall Seal the Heavens that first made her appearance in Book 9. She is a part of Chu Yuyan's soul that was taken by and put in in symbiosis with Han Bei's soul, until Meng Hao separated them.
She is a beautiful, slender and elegant young woman with a natural gift for cultivation, especially when it comes to alchemy. She had a boyish disposition, not the least bit graceful and subdued. After undergoing her immortal tribulation, she became even more beautiful, otherworldly and bears a striking resemblance to Chu Yuyan.
When Yan'er was younger she was shy, but as she grew she developed an almost tomboyish personality due to being pampered by Fang Mu (Clone).
Chu Yuyan's soul that was sent out into the mortal world of Planet Vast Expanse into a mortal woman's womb to be reincarnated. Eleven years later, she was found by Fang Mu (Clone) and taken as his one and only disciple. 
Han Bei sent Chu Yuyan's soul out and Meng Hao put her into a woman's womb in the mortal world to begin the cycle of reincarnation.  Later on when Yan'er had reached eleven years old, Meng Hao's clone, Fang Mu (Clone) appeared to accept Yan'er as his one and only apprentice. 
Yan'er showed exceptional talent in cultivation, still not near Fang Mu's; however, her true talent is in the Dao of Alchemy, much like Chu Yuyan's. Fang Mu taught her various daoist magics and also many of his alchemic techniques.
At one point, Yan'er went to a disciple gathering where disciples from the eight sect were also present. There, she was kidnapped by a degenerate who hoped to "use her as a cultivation furnace" (rape). However, the Blood Mastiff came to her rescue and killed the man's Dao Realm Dao Protector. The man turned out to be the grandson of the future Eighth Paragon of the Eighth Sect.  Needless to say, Meng Hao slaughtered anyone who had evil thoughts regarding Yan'er. 
Eventually, Yan'er started developing feelings for Fang Mu. This became even more apparent after Meng Hao told her about the story of Chu Yuyan and how she affected him. This could be a cause of her previous love for Meng Hao or could be feelings she developed in this life.
Yan'er became a bit reserved and had a thoughtful expression on her face most of the time once Meng Hao told her the story of Chu Yuyan, almost as if she was remembering things.
The good fortune in the form of the energy of innumerable bell tolls and eighty heavens allowed Yan'er's cultivation to tremendously increase, most likely putting her at the great circle of the Immortal Realm.
After Meng Hao started his reincarnation cycle, and was believed to have died, Yan'er vowed that she would follow in her master's footsteps. She ended up becoming a Chosen almost at the same level as Meng Hao after she summoned the Ninth Heaven in all of the nine sects. After reaching the Dao Realm, she decided to, also, challenge the Transcendence Path.
Yan'er found Little Treasure (Fang Mu (Clone)'s ninth reincarnation), married him, and lived a happy life. Eventually, she became pregnant with his child and their child together was named Perfect. They lived happily for a decade, until the wrath of the will of Allheaven attacked the entire First Continent. Yan'er lost her cultivation base and was forced to scar her face to avoid a horrible fate due to the abundance of vile men. One day, Perfect was kidnapped and Yan'er was almost raped. Something snapped inside Little Treasure and he killed one of the assailants by tearing his throat out with his mouth. Perfect never returned but Little Treasure and Yan'er found the corpse of the four men. Still, they felt she was safe (Meng Hao saved her from being raped and took her to the Ninth Continent as his daughter, which she technically is). Yan'er realized that this was the work of some supreme expert who was able to keep his cultivation even in the first continent and decided to let Perfect go as this was the stroke of an unimaginably incredible fortune for her. Also, she feared her daughter being put in the same situation again and she realized that Perfect could never live a happy life in their current circumstances. Afterwards, Little Treasure and Yan'er became ruthless to be able to survive in their cruel world.
As the cold kept getting worse, both Little Treasure and Yan'er kept getting closer to eventually freezing in their cave. Along with other people, they ventured out to find a new, only to get caught in an avalanche. All died, except Yan'er who pulled Little Treasure out of the snow, unconscious and fed him her blood to get him warm. After returning to their cave, Little Treasure realized that he had dropped his ninth seal sculpture during the avalanche. That night, Yan'er went back to the site of the avalanche and retrieved the sculpture, although at the cost of almost entirely diminishing her life force and suffering frost-bite all across her body. Somehow, she managed to return back to the cave. Her life faded away in the arms of Little Treasure as she finally spoke her feelings to Fang Mu.
After her soul exited her body, Yan'er destroyed the other part of her soul that was with Han Bei and the part with her memories as Chu Yuyan. She entered the reincarnation cycle willfully, having lived a content life.