Arakna Hollows:
Whhaaaaatt, why? Did they at least get together in the novel Moonlight Mystique?
You mean Senyu and Cheng Qin?
Qing Li (or Qing Lin in the drama) almost killed Cheng Qin (Hong Ruo in the drama), removed her demon core and opcupied her body. However Cheng Qin was still alive. Both Qing Li and Cheng Qin shared Cheng Qin's body but Qing Li's soul most of the time dominated Cheng Qin.
On the last battle, Yuan Qi stood in front of the purgatory which sealed the devils, ghost races with immortal soldiers and demon troops. Qin Li led the devils to break the seal from inside.
Yuan Qi lured Qin Li out by threatening her that if she wanted to kill Yuan Qi for her revenge she had to come out, otherwise he would go away and she could have no other chance to kill him.
Yuan Qi and Shenyu tried to kill her and she revealed that Cheng Qin was still alive and shared the body. Qing Li still loved Shenyu and persuaded him to follow her. For a blinking moment, Cheng Qin woke up and told Shenyu to kill her/Qing Li. At the end he hit her heart with his spear and Yuan Qi used his Chaos power to burn out Qing Li's devil soul. Shenyu used similar technique that Jing Jian used to elevate his power level. Then all of them were "killed" by Yuan Qi's sword. It is almost impossible for them to reincarnate.
There are only 82 chapter of Moonlight Mystique published online and it doesn't mention about ShenYu or Cheng Qin.