The main character is the villainess, no doubt. However, there could be a mentor - like figure in the novel. This person could be guiding her, either towards more darkness or towards the light. And there may be friends or allies that she meets along the way. These characters would add depth to the story and her journey through her dark side.
One of the main themes could be redemption. The villainess might strive to overcome her 'dark side' and find a new path. Another theme could be power struggle, as she may be dealing with others who oppose her in her journey.
Since I don't know which 'the dark side novel' you're referring to, I can't tell for sure. But usually in a novel about the dark side, there might be a protagonist who is either fighting against the dark side or being lured into it. There could also be an antagonist who represents the dark side fully.
The villainess herself is a main character. Her character development from being a typical villainess in the original concept to something more complex is a central focus.
Without having read the 'Dark Side of Valor A Novel', it's difficult to name the main characters precisely. But it's possible that there is a central character who is on a journey to understand the true nature of valor. Along the way, they might meet other characters like comrades in arms who have different views on valor. There could also be a character from the enemy side who makes the protagonist question their own ideas of what it means to be valiant, adding to the exploration of the dark side of valor.
There could be her family members like her parents. They might play important roles in the story, either supporting or opposing her at different times.
There might be an older character, perhaps a grandparent. This character could provide wisdom and a connection to the past, and their views on love could contrast with the younger generation's. They could have stories of their own love during more peaceful times in Syria, which would add depth to the exploration of love in different eras.
I don't know for sure since I haven't read it. But it could have astronauts as main characters. They are often the ones exploring the moon and would be likely to be central to a story about the dark side of the moon.
One important character could be the villainess' former rival or enemy from her past life. Their interactions in this new life could be full of tension and drama. Also, there may be a mentor - like figure, perhaps an older witch or a wise noble, who helps the villainess understand her past and change for the better. And of course, her family members, whether they are supportive or part of her past problems, are important characters too.
Since I haven't read the novel, I can't say for sure. But typically, there would be the villainess herself. There might also be a hero or heroine who opposes her. And there could be side characters like her servants, allies or enemies in her villainous plans.
Typically in a 'kill the villainess novel', you'd have the titular villainess. She could be a cruel and powerful figure. Then there's the main character who aims to kill her. This character could be a wronged party, perhaps a former servant of the villainess or someone from a rival family. There may also be other characters like a love interest for the main character who could either help or hinder the mission to kill the villainess, and perhaps a mentor - like figure who gives advice on how to take on the powerful villainess.