David said that his goal was to keep Diana's appearance in the film as a silhouette. When asked about how challenging it was to keep Diana in the dark he said "Very challenging because I didn’t want to cheat. I had to storyboard all of it just to make sure that she was truly a silhouette. At first I was working with a storyboard artist. He would draw her with a rim light on her and I was like, “No, we can’t shoot it like that because that’s cheating.” So I had to do my own storyboards and really figure out how we could always keep her as a true silhouette. When she grabs Bret, I had to think about, “If he uses his flashlight like this to bang on the handle, if she grabs him when he’s up here, then the flashlight is pointed backwards creating a silhouette so that she can actually grab him.” It was really hard to figure out exactly how to get her on film." Diana was originally suppose to be more of a demonic presence but James Wan suggested that she have a human background so she could have a relationship to Sophie and add to the connection to the family.
In an interview, when asked about the casting of Diana, David said "...I figured she would be pretty still but once I met Alicia, we met Alicia just to have her as a stunt person for whoever would play Diana. But when I met Alicia and she showed me what she could do, because she’s a dancer and she has full control over her body, it was like, 'Oh, this is really awesome. So let’s have Alicia play Diana the whole time and we can really turn her into this ferocious, animalistic creature almost.'”
In the 2016 film Lights Out, Diana is a mysterious figure that attacks people in the dark. It is revealed that she was a woman in a mental hospital that had a serious skin condition that prevented her from being in any light. Doctors had began performing experiments on Diana, but killed her by overexposing her to light. She latched her self onto her friend Sophie, killing anyone trying to help or be with her. She begins to attack Sophie's family. After several close encounters with Diana, Sophie's daughter Rebecca realizes Diana is in control of her mother. Rebecca convinces her boyfriend to help her defeat the vengeful entity. When Diana attacks Rebecca in the basement, Sophie kills herself, causing Diana to disappear as her entire existence relied on the life of Sophie.
The character has been well received. Some have said that she'll become a staple in horror movie lore. John Squires of Bloody Disgusting praised the character saying:
"Exploiting our collective fear of the dark, David F. Sandberg’s debut feature Lights Out introduces a creepy new villain who goes by the name Diana, and if you had any trouble sleeping after the film, it’s damn sure because of her. Bathed in darkness throughout much of the movie, with only her piercing eyes illuminated, Diana is a horror villain who quite literally exists only in the dark, appearing when the lights are turned off and vanishing back into thin air when they’re turned on."
"With her wild hair and impossibly long fingers, Diana cuts a silhouette that is, in and of itself, scarier than most movie monsters could ever wish to be, but it’s the unnerving performance of the actress tasked with bringing her to life that may have ensured the character goes on to become a franchise-starting horror icon. And setting her apart from recent female villains like the titular Mama, the Insidious franchise’s “Bride in Black,” and the four-armed Myrtu from this year’s The Other Side of the Door, Diana was actually played, in a refreshing twist, by a female performer."
Maria Bello, who portrays Sophie in the 2016 film, compared Diana to Freddy Krueger and Jason Voorhees saying "I think people at Comic-Con will be dressed up as Diana next year. Just the way she moved her hands and shoulders I think created an entire beast. I think her creature will transcend time and will be like a Freddy Krueger or a Jason."