Lucy Lawless has shifted from warrior princess to witch in WGN America's "Salem," a fictional recounting of what happened in the 17th century village that held the witch trials. And her character, Countess Marburg, is as far from Glinda the Good as possible. She is even more evil than the Wicked Witch.

Truth be told, this is the most malevolent villain Lawless has played to date, and that includes her role as the devious Lucretia in Starz’ “Spartacus” franchise.

"Lucretia was a survivor," Lawless told FOX411. "It was easy for me to justify her behavior. She was a survivor in a very tough environment. Then she lost her mind when her husband was killed because he was everything to her. So she had that redeeming quality of absolute love for her husband. But in the case of the countess, she's bad, not just to the bone, but to the marrow."

The Countess Marburg is a very powerful witch, who is a part of an ancient line of German witches. Not a descendant, but an original. And on Sunday night's episode, "The Wine Dark Sea," which Lawless described as "a juggernaut of horror," there is a big reveal of the hideous method by which she stays young.

"The character is so morally corrupt by society's standards, not only today, but in those days, and, for me, that presents ethical issue," Lawless said. "But because this is horror, and it's beautifully realized horror, I can't let my personal feelings get in the way. Honestly, I really had to consider the morality of even shooting some of these things. It's pretty hard-core stuff."

Lawless' interest in the horror genre developed at a young age. Her father would tell vampire stories in order to keep the kids quiet in the back of the car when they took long drives. So is it any surprise the first movies she watched were horror films? She joked, "I learned how to fight vampires at an early age."

Even so, when it came to playing Countess Marburg, Lawless didn't look to any characters from previous horror projects to craft her role. Rather, she said it is a result of growing up in a large family. She has five brothers and one sister.

"There was a lot of competition for things like cookies-- food in particular-- so you would have to cheat, lie and manipulate to get your share," she recalled. "We would torment one another and razz one another mercilessly. Often, I use the razzing skills I developed as a kid in the show to sort of nah-nahny-nah-nah another character without being seen to."

When "Salem" wraps production in Louisiana shortly, Lawless will return to New Zealand, and jump right into another horror project, "Ash vs. Evil Dead,"  which is being executive produced by Lawless' husband Robert Tapert, of "The Evil Dead" fame.

And there is a funny story there. When Lawless was 17, her first boyfriend took her to watch a "really great film" called "The Evil Dead." Not too far into the film, there is a scene where a girl gets raped by a tree. This incensed Lawless so much, she stomped off and didn't watch the rest of the movie.

"I remember saying that the people [whoever] made this movie were misogynists, and I never wanted to see anything from those people again," she said. "So, before I know it, I'm married to one of them. That's one of those never-say-never moments. That's crazy, isn't it?"

"Salem" airs Sunday nights on WGN America.

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