Joan Allen — best known for playing heroines in The Contender, The Crucible and Face/Off — jumped at the chance to go bad in the TNT miniseries The Mists of Avalon (which concludes tonight at 8 pm/ET).

"It really appealed to me when I found out they offered me the role [of Morgause]," the 44-year-old three-time Oscar nominee tells TV Guide Online. "My agent said, 'It's a villain,' and I said, 'Send me the script! Send me the script!'"

In the two-part epic, which is based on Marion Zimmer Bradley's retelling of the Arthurian legend, Morgause lies and schemes her way to power. Co-star Anjelica Huston — Morgause's rival and sister, Viviane — was taken aback by Allen's dark turn. "Let me tell you, when she's flying down the stairs at you with a dagger in her hand, it's daunting," she recalls of Mists's climactic scene. "I think she was really superb in this — and gleeful. You could tell how much fun she was having with it."

Despite the accolades of her peers, the Rochelle, Ill. native still thinks of herself as "a Midwest girl who comes from a little town of 8000 people." In fact, although Allen may now call New York City home, she doesn't indulge in any star treatment. "I still take the subway all the time and ride buses all the time," she reveals, adding that only on occasion does she get recognized. "You know, maybe a couple of times a day, someone on the bus will say something, but it's very fleeting. It's complimentary and it's nice."