Not much is known about the demon due to the ambiguous nature of the movies. The demon was summoned by a coven of witches, to which Lois Featherstone belonged, who made a deal with the demon for wealth and power. The demon's intent was to befriend a young Kristi Featherston, the family retreated to Lois's in Moorpark, CA. The demon followed them and killed Julie and Dennis, the coven then brainwashed the girls so they didn't remember anything. The demon then stayed with Lois, who eventually died followed by Kristi (who was an adult) giving birth to a son named Hunter. After haunting Kristi for a couple of months they learned that the coven had made a deal with the demon, they offered the next male born into the family for wealth and power and Hunter is the first male born since the 1930s. The demon was passed onto Kristi's sister, Katie, initially haunting her but then moving on to possession. A possessed Katie then killed her sister and brother in law, then took Hunter fulfilling the demon's desire. In the fourth film, Katie (possessed) moved across the street from the Nelson family and the Nelson's took in her "son" Robbie, the demon followed Robbie and started to haunt the family. It is then revealed that Wyatt (their 7 year-old boy) is in fact Hunter, and Katie/Entity put him up for adoption for the duration of his younger years after murdering his parents as a baby, returning once Hunter/Wyatt reached the right age. Katie/Entity and Robbie broke into the house, killed the family and took Wyatt/Hunter, the demon finally getting what it wanted.
The demon is shown to be powered by fear and grows stronger and more aggresive as it feeds on the fear of others. He hates to be given attention from the camera and being acknowleged by anyone (Except Kristi). The first major theory came from Ali Rey who looked up the events and traced it back and made the theory of male born baby sacrifice. The theory is that Katie's great grandmother had wanted money/power or something she desired and made a pact with the demon to sacrifice the next male born baby in the Featherston line. This theory is most likely because the demon does kidnap the first male, Hunter Rey, in Paranormal Activity 2. Another theory made up comes from Dennis in Paranormal Actvity 3. The theory came from him researching a coven of witches from a symbol the demon wrote in the closet space in Julie Featherston's house. The coven of witches had brainwashed girls into having babies and forget about it laiter on. The great grandmother had most likely joined the coven and ensured them the first male born for power. It is unknown what they did to Kristi as a child but they somehow knew Kristi was the carrier of the male born child. A hint is shown briefly in Paranormal Activity 3 when Dennis checks the closet space, Hunter's name is shown backwards, indicating that it knows the future. Lois Featherstone also joins the coven for an unknown reason and has no remorse for her daughter or her granddaughters. This is most likely because Julie was created when the coven brainwashed Lois into having a child and Lois grew to hate Julie because Julie is not the first male and was made from most likely a rape from an unknown man.