She is portrayed by Deidre Hall.
In perhaps one of the most talked about storylines in the show's history, Marlena was actually possessed by the Devil during the 1995-1996 season. In her possessed state, Marlena (called MarDevil by fans) gained the ability to shapeshift, morphing into a panther and even transforming herself into her rival, Kristen DiMera. She was later successfully exorcised by her husband, John Black, who is an ordained minister.
Marlena turned heel once again during the 2003-2004 season, when--in another odd storyline--she became a serial killer known as the Salem Stalker. Under a cloak of mystery, Marlena began her killing spree with Abe Carver, then later killed Jack Deveraux, Maggie Horton, Cassie and Caroline Brady, and her ex-husband Roman Brady during his wedding. At a circus, Marlena released a tiger from its cage and sent it to attack Tony DiMera. Tony ends up in the hospital barely clinging to life, but it is in that moment that Marlena's heel turn is cemented and she is revealed as the serial killer. Disguised as a medical doctor, Marlena continuously drugged Tony to finish the job.
Now an established villainess, Marlena set her sights on Doug Williams after actually confessing to one of her murders to a priest. Doug found out that Marlena is the killer during a confrontation, which led to Marlena killing him at Tom Horton's grave. A bloody note with Marlena's name on it is found by Alice Horton, and because of this, the evil Marlena chose her as her next victim. Marlena laughed evilly during a verbal confrontation with Alice, while stating that she has to kill her, which she does by choking her with her world-renowned doughnuts. Marlena later confesses to the murders, but the theory is that she could be possessed again. While it turned out to be true and she was exorcised once again, it was not a factor into Marlena's heel persona, and she was arrested for the murders.
Marlena is shot and killed on the rooftop of the prison, but--in yet another crazy twist--not only was Marlena still alive, but so were the people she killed. They were all found on an island called Melaswen (New Salem spelled backwards). In another twist, it turned out that Marlena wasn't a serial killer; she was kidnapped by Andre DiMera, the nephew of the villainous Stefano Dimera, and made to believe by Andre that she was killing her friends and family.
- Marlena Evans became the first soap opera character to be possessed by the Devil.