The bright moon and gentle breeze. Xiao Xingcheng is a delicate, Daoist priest who makes a particularly nasty enemy in Xue Yang. He gave his eyes to Song Lan after Xue Yang blinded Song Lan to get back at him. His parallel in our main couple would be Lan Wangji (with both Song Lan and Xue Yang taking the part of Wei Wuxian). He's kind, trusting and deeply competent with his sword. I like him a lot.
"Xiao XingChen left the mountain alone and had no family. He only had a friend that he met afterward, named Song Lan... Both of them wanted to build a sect that valued common ideals instead of blood ties, which made them the closest and most like-minded of friends. The people of the time described them as such - Xiao XingChen the bright moon and gentle breeze; Song ZiChen the distant snow and cold frost."
Killed himself after learning Xue Yang tricked him into killing innocent people and his life partner Song Lan. Has no desire to be reincarnated.