Stern head of the Nie Clan, MingJue has been dealt a bad hand: his blade, Baxia, is slowly disrupting his qi and driving him mad. He knows it's happening - happens to all the Nie Clan who take up blades (probably their butcher background), but he can't do much about it. Had a soft heart for Yao at one time; no longer likes or trusts him (with good reason) now.
"His brother, Nie MingJue, was extremely resolute when carrying out orders, quite renowned in the cultivation world. Although the brothers were not born from the same mother, their relationship was quite solid. Nie MingJue had always taught his younger brother with extreme harshness, particularly caring for his studies."
Beheaded by Xue Yang in Jin Guangyao's secret room after a qi deviation brought him down. It's his arm (or sword) that's causing mischief and mayhem in the first episode, trying to reassemble his corpse