Nix - Queen of Wands
People either really loathe Nix because she's too shallow or they love to hate her, and I think it all depends on if you--the reader--has personally met someone like her. She's a very deep woman that we only see in glimpse. I could easily write entire books about her, and have one planned in the coming war.
The thing about good villains is that they're not pure evil. Nix has made a lot of evil choices and she will never be able to be "saved". I'm sorry, but she just can't. She did too much damage. She'll have to try again in the next lifetime. But... she did it because, in her mind, she is the hero.
Truth about the Marks
So much of the history of Ilana (the moon we're on) surrounds the Marks of power; tattoos that appear when a person becomes an adolescent.
The Marks are the reason for the blood purges, which is how Nix lost her family. She was married and had kids when her Mark "changed" and she was cast out onto the ice with nothing more than the clothes on her back.
She's not the only one. Far from it. In order to keep the Mark strong, the seven Great Families chose to keep their blood "pure" by only marrying within their tribe.
Understand, these seven tribes are quite large. There's no real concern about incest or the genetics.
Path of Revenge
Nix started down this road seeking revenge for herself and all the others who were thrown out.
But she soon discovered a liquid metal in the blood of those with the Mark and had an idea that this metal was more than it appeared. She thought that it gave people more than just Marks of power. It did more than allow the bearer to summon fire, or manipulate the sands, or heal, or capture lightening.
Her "path of evil" didn't start off completely evil. She went to the Shankara, intent on destroying them, but failed--on purpose. She'd just discovered the metal and wanted to capture more people with strong Marks so she and her team of scientific investigators could research their blood.
She succeeded, but gained a name for herself in the process. She does still want them all dead. She lost a husband she loved and children she cherished.