Big Spoiler
I think he's not actually dead, if I remembered the novel right. I think, if I remembered right, that mysterious guy that met with nie linglong was actually him. And then he pretended to be dead and continued to do his secret mission for revenge or something (I didn't really understand the reason why back then but i think it was for his lover or something like that).
Not quite sure about the specific details, but that's the gist of it i guess. I may be wrong or i got some things mixed up tho cuz it had been so long (for several years) that I read the novel and I even skipped some chapters haha.
Yes, Nameless Nie want to take revenge on people in independent state because his lover (Miao or whatever her name is) is an outsider, you know that independent state won't allow marriage with outsider. She also the leader of the real Rose of Death, that's why Woriless Nie have the leader's ring, she gave it to her. Nameless Nie lover supposed to be dead because she is Rose of Death leader, and they are being hunted down by The arbitration council. So, he kill the previous arbitation council president because the death order issued by him, so the current president is Yi Lingjun which Woriless's master. It's also related how she being hunted back then. They know she had the ring, but on another part, her grandpa have plan to rebel against the arbitration council (with Si Xia), she disagree and challenge her grandpa (which her grandpa would back down if she win). But, there's accident which she hurt her grandpa. She panicked and run. So, she though she kill her grandpa, she run away from the martial union that chase after her under Si Xia order and Si Yehan save her like we know. Well, they know the grandpa died because of Woriless when actually the one who make it worse is her brother in disguise who come to harm his grandpa (which half hearted because he is his family), so that's actually misunderstanding. oh her grandpa is alive. Nameless want to kill his grandpa because he oppose his relationship the most, so do his parent (the reason why he join hand with the bad guy to harm Nie family).

Omg not the brotherrrrr omg