Deconstruction: Religious cult Symbols of The Devil Inside

The main religious symbol in The Devil Inside is what is known as The Cross of St. Peter. 
It is called this because Catholics believe that St. Peter was crucified upside down as he did not deserve to be crucified the same way Jesus was.
This symbol is also worn by a lot of Satanic followers because it symbolizes mockery and rejection of Jesus.
It also represented unworthiness and failure and reverence of Christ

In the film, this cross at first is thought to believe the original mark of Jesus, the Latin cross. When she carves these crosses into her arm you realise that from your point of view they are normal crosses, but from her point of view, they are actually St. Peter crosses. She also makes a similar mark on the inside of her bottom lip, which is obvious it is a St Peters cross.

These marks are also referred to as Stigmata (Greek word for marks) Paul talks about these marks in Galatians and many Christian followers claimed they did not know anything about what Paul was saying. But Paul was actually referring to when a person allegedly possesses marks on his or her own body, which Maria Rossi did. 

Deconstruction: Religious Cult Symbols in Sinister

SINISTER:

The plot of Sinister is based around a Pagan Sumerian deity named Bughuul, who would kill entire families so that he could take their children into his realm and consume their souls. He mainly targets children because they are extremely vulnerable to dark magic, and are easy targets because they don't have an extensive knowledge of this world and don't know right form wrong. 

This picture is of one of the children that lost her soul to Baguul. In the film he is often referred to as "Boogey Man" which is often used to make children behave. 

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This is the symbol of Baghuul which is shown throughout the film, mainly on the super 8 footage that Ellison finds in his attic, on some footages this symbol is harder to notice than others. 

A specialist in the film sends this to the writer as a reference to the history of Baghuul. These were drawings done a long time before the murders started, both feature the symbol of Baghuul, however the one on the left has a dog in it and the one on the right has a snake in it.
In the film there is a scene just after the writer watched the super 8 tape of the family drowning where he found some drawings on a box lid, underneath the lid however was a snake, just like the picture on the right.
Another scene features a dog, where the writer goes out into the garden where the last family was hung and he gets startled by a rottweiler, again exactly like the picture on the left. 

Early Christians believed that Baghuul actually lived in these images, and that they were gateways into his realm. They believed that he would take posession of those who saw the images, and cause them to do terrible things like murder their family. Some believed that he could also abduct the viewer into the image.