Abalam is the antagonist in The Last Exorcism. He is a demon who has possessed Nell, a ranch hand's daughter. In the film, he was played by actress Ashley Bell, who portrayed his vessel, Nell, when she was under possession.
What has happened in the film is that Nell's dad is finding his livestock killed overnight and the house being wrecked. He believes a demon is at work and calls Marcus, an exorcist, and Lous Sweetzer, Nell's dad, says that it is a particularly tough demon they are dealing with. Nell, Lous' daughter, seems possessed: she wakes up with blood on her dress and she is seen with knives and other weapons. Marcus has only one problem, he doesn't believe in demons or possession. Thinking it is fake, he challenges the demon to announce himself, while possessing Nell. The demon introduces itself as Abalam and says Nell is burning when he uses her. Abalam kills the family's cat when possessing Nell. Later on, Marcus, still not believing, goes to a bar when he talks to a man named Logan who slept with Nell but Logan says she's not pregnant.
Later on Marcus challenges Abalam to come forth and talk with them and Abalam says he will talk only if they are quiet when he breaks Nell's fingers. So he breaks three of her fingers but Marcus tells him to stop. Marcus meets a priest, Manley, who tells them he can help. But they come back to the house and find it wrecked, with Satanic imagery everywhere. They hear chanting, and Marcus finds a cult in the woods worshipping Abalam. Marcus sees Manley, the cult leader, pull a demonic foetus from Nell and throw it into the fire, where it grows. Then Marcus runs out with a cross to fight the cult. Marcus' crew are found and Iris the camerawoman is chopped up and Daniel, the editor, is chased but then Caleb, Nell's brother comes out and kills him.
In the events of the sequel, Nell appears in the home of a couple who protect her, despite her being mad. Its clear Abalam is after her again and is inciting her to kill. Nell gets enrolled at a university but she is teased by the other kids.
One day the footage filmed by Marcus' crew is found and released on YouTube, which angers Nell because of her sudden fame. When Abalam appears to her as her doppleganger, and her dead family, and seduces her to darkness again, Nell snaps and starts a demonic fire which kills her tormentors. Then it is revealed Nell is again possessed by Abalam and she is alright with it. She gets in her car and drives off, giving an evil grin and leaving a trail of chaos and destruction in her wake.