The Sun in the Dark Episode 16

To avoid being separated from Bai Yi Xi for all eternity, Wan Gu Chen resolutely absorbed the power of the Night God into his body, but fainted because he could not withstand it. Upon waking, he discovered that Bai Yi Xi had been completely taken over by the Night God and had lost her sense of self. When she regained consciousness, Bai Yi Xi begged Wan Gu Chen to kill her to spare her from continued suffering and struggle. Wan Gu Chen’s heart was torn apart, and in the end, he had no choice but to draw his sword against her. Though his heart was breaking with grief, he could not bear to see his beloved continue to suffer. He realized that the power of the Night God had fused with his own body and understood that only by fully absorbing the power in the next life could he save Bai Yi Xi. Wan Gu Chen transformed into the Night God, Ye Chen Yuan, and Hua and Ying recognized him as their new master. Bai Xiao Ying finally understood that Ye Chen Yuan had transferred the power of the Night God to himself to save her. Ye Chen Yuan hoped Bai Xiao Ying would kill him, for otherwise the Three Realms could never find peace, but Bai Xiao Ying would rather forfeit the Three Realms than let him die. Ye Chen Yuan embraced Bai Xiao Ying and, gripping her sword, pierced his own body. Bai Xiao Ying watched helplessly as he vanished, overcome with grief. Bai Xiao Ying returned to the Immortal Realm, where everyone praised her for slaying the Night God, and the Immortal Lord hoped she would become the God of War. Bai Xiao Ying told the Immortal Lord that Ye Chen Yuan was actually Wan Gu Chen, leaving the Immortal Lord utterly shocked. (Source: Chinese = zuiai.tv || Translation = Deepl)