Song Lan has been waiting for thousands of years for Xing’s soul to reincarnate, protecting the world from Hell spilling over as best as he could. He waited, he grew tired.
Then a fake priest nearly fell out of a window, and while saving him, Song Lan came face to face with one Chief Xiao.
Source: What The Heart Wants (The Heart Gets), by Aamukaste – 陈情令 | The Untamed (TV), 魔道祖师 – 墨香铜臭 | Módào Zǔshī – Mòxiāng Tóngxiù, 魔道祖师 | Módào Zǔshī (Cartoon) [Archive of Our Own]
The perfect Guardian fusion, I only wish this was a million words long…