These markings and symbols appear throughout the franchise of the Paranormal Activity movies.
Paranormal Activity 2Before the conclusion of Paranormal Activity 2, Kristi is dragged into the basement. The next day, while Ali is left to take care of Hunter, she opens the basement door. She fires up her camera to capture what looks to be deep scratches on the inside of the door. While debatable, the consensus among multiple sources on the internet is the word "MEUS" is scrawled on the door. The word meus in Latin means "mine".
The appearance of this word, and the occurrences regarding the basement, lead us to believe that the demon's power emanated from there.
Paranormal Activity 3The first appearance of the thaumaturgic triangle is in Paranormal Activity 3. It appears to be drawn with black crayon inside the hiding space connected to the girls' bedrom. It also has the letters M, C, and L around it. The second appearance is near the end of the movie when Dennis is trying to find Julie in Lois' house. In Lois' dining room, on the wall where the painting of the unicorn was, a smaller, neater triangle appears. It does not have the same letters on it, but it should be noted that young Kristi was seen earlier coyly studying the painting, and we can assume that she was looking behind it.
A pentagram appears in the same dining room on an adjacent wall where another painting hung before Dennis started looking for Julie. Both symbols directly imply that either satanism or witchcraft is being used by Lois.
Paranormal Activity 4
- In Paranormal Activity 4, there is the thaumaturgic triangle in the sandbox. This is revealed later when, on the laptop, it is shown that while Alex was sliding down the slide, she pauses the video and shows Ben the symbol. Earlier in the movie, but not chronologically, Robbie drew the same thaumaturgic triangle on Wyatt's back to 'allow him to see his friend'. Though it is not sure whether Robbie did this so Toby could possess Wyatt or just so Wyatt would be allowed to see Toby. Whether or not, this still is shown.
Even earlier in the movie, Alex was walking around and noticed some toys. She followed them and opened Wyatt's closet door. On the door, there was a large marking that messily wrote HUNTER. Alex sees Wyatt come in and asks him who wrote it. He simply shrugs, remarking 'I don't know'. This implies that either Wyatt was possessed OR Katie went into his room.
The triangle means that the demon has to sacrifice the first boy born in the family.