Our hero! He's died once already (first episode - it's not a spoiler) and has been brought back permanently by Mo Xuanyu to right past wrongs. WuXian is a brilliant, inventive cultivator but he's been forced to embrace the dark arts - namely reincarnating the dead to do his bidding - in order to survive. Kind of oblivious to Lan Wangji's steadfast love for him, but it's starting to dawn on him.
"It was widely known that, although Wei WuXian’s surname was not Jiang, he was the leading disciple of the sect leader of the YunmengJiang Sect - Jiang FengMian, and also the son of his friend who had passed away. In fact, the sect leader regarded him as his own child."
Transferred his golden core to his brother Jiang Cheng while his brother was unconscious. Died (badly - devoured alive by corpses) from the backlash of the Stygian Tiger Seal in the manhua & book, not from falling from the cliff.