Diana Walter

"Keep the lights out."

- Diana

Diana (full name: Diana Walter) is a malevolent entity and the main antagonist of the 2016 horror film, Lights Out. She was originally a human girl who was diagnosed with a skin condition which caused her to negatively react to light. After being killed in an experiment gone wrong, she became a vengeful ghost who mainly kills her victims in the darkness.

Short film
The short film revolves around an unnamed woman (portrayed by Lotta Losten) being haunted by the spirit of a mysterious girl that only becomes manifest in the absence of light. The film ends with the ghost girl turning the lights off, and presumably murdering the woman.

Early life
At age 12, Diana was taken to a mental hospital after she had manipulated her father into killing himself via mind games. She was diagnosed with a skin condition that caused her to react negatively to light, and she had violent tendencies. While at the mental hospital, Diana met and befriended Sophie, though as Becca pointed out, she most likely manipulated her mother into thinking that they were friends.

Eventually, experiments were conducted on Diana with healing her skin condition as the objective. Unfortunately, the experiment goes awry, and Diana is reduced to ashes. Since then, her spirit had latched itself unto Sophie, and only becomes manifested when she was off her medicine.

Present Day
Some years later, Sophie's husband, Paul was working late at night at a mannequin shop. When Martin, his son, was informing him on Sophie going through one of her episodes, Diana kills him. Later on, it's revealed that Diana also murdered the children's biological father when he was trying to get his wife stable. Diana then manipulates Sophie into thinking that he left her. Throughout the film, Becca and Martin attempt to free their mother of the malevolent spirit's power, which invokes the wrath of the deceased girl. Diana began to manifest herself as a sentient shadow who could only be dispelled by light. As such, the two siblings attempt to keep the lights burning throughout the house; however, a power outage results, causing the children to enter the basement in order to restart the generator. Diana then slams the door on the two, and meanwhile Sophie was looking for the kids until she sees Diana backing up from the light. Sophie immediately told her not to hurt her kids that they don't know any better, however Diana threaten Sophie. As the both of them got into an argument, Sophie told her not to threaten her. Diana got into a temper tantrum and knocks Sophie unconscious when she was trying to take her medicine.

Bret, Becca's boyfriend, manages to get to his car, and he alerts the police about the seeming domestic disturbance. Unfortunately, the two police officers get effortlessly slaughtered by the vengeful ghost, and she attempts to brutally murder the two children, thus going against Sophie's demand of sparing them. Regaining consciousness, as Diana was about to kill Rebecca, Sophie gave her a warning not to hurt the kids. Rebecca told her mother that Diana was the one who killed their father. As Sophie shoot at Diana, Diana mocks telling her that that won't hurt her. Sophie obtains a gun, and she reminds Diana that without her, she couldn't manifest in the physical world. Diana lunges at Sophie to stop her as she pulled the trigger onto herself, and she shatters into pieces. The film ends with the ambulance arriving to tend to the protagonists' wounds. Without any warning, the lights began to flicker, but Brad assures them that Diana is truly gone.

Abilities
After her death, she had latched herself to Sophie's mind; as long as Sophie was alive, Diana could project herself in the world of the living. Hypothetically speaking, if Sophie were to die, Diana would no longer exist as her ties to the world would be severed in the event of Sophie's demise. Additionally, she can be temporarily expelled from her mind as long as she took her medication.

Diana can only physically appear in the absence of light, a trait that was passed on from her former life. When she was human, her skin reacted negatively to the slightest hint of light, going as far as to burn her. In addition, she has near-superhuman strength and agility. However, Diana can be seen under black lights; this is proven when Martin found a black light when he and his sister were trying to turn the generator back on.

Trivia

 * Alicia Vela-Bailey portrays the ghostly Diana, whereas her human counterpart is portrayed by Ava Cantrell.
 * Diana was created through the use of a photorealistic prosthetic suit.
 * Originally, Sophie's suicide wasn't supposed to work; David Sandberg, the director of Lights Out, explained that the ending was changed after the test audience reacted negatively to the uselessness of Sophie's sacrifice.
 * As such, a sequel has been announced in order to fix the ending.
 * Diana shares a few similarities with Mister Babadook the titular antagonist of the horror film of the same name. Both are demonic entities that tend to be shrouded in darkness, they both cause one of the leading characters to suffer mentally, and they both can be taken as metaphors for a larger idea. For instance, some suggest that the Babadook represents grief and how strong it can get if left unattended, whereas Diana is believed to represent depression as she seems to manifest whenever Sophie is having mental issues.