As an expert in the field of supernatural fiction and its impact on popular culture, I can provide a detailed analysis of the question you've posed. It's important to note that the question refers to a fictional scenario, specifically from the TV series "Supernatural," which revolves around the lives of two brothers, Sam and Dean Winchester, as they battle various supernatural entities.
In the context of the show, "demons" are malevolent supernatural beings that can possess humans, causing them to act out of character and often commit violent acts. The episode "Born Under a Bad Sign" from Season 2, as you've mentioned, features a significant plot point where Sam Winchester is possessed by a demon that had previously possessed another character, Meg Masters.
The demon's possession of Sam is a pivotal moment in the series, as it tests the bond between the Winchester brothers and showcases the lengths they will go to protect each other. The demon's ability to bind itself to Sam using a spell, indicated by a brand on Sam's arm, adds a layer of complexity to the situation. This binding spell makes the exorcism process more challenging, as it is not a straightforward matter of casting the demon out but requires breaking the magical bond first.
The demon's actions while possessing Sam are particularly brutal. It kills Steve Wandell, attacks Jo, and inflicts severe physical harm on Dean. These acts serve to heighten the stakes and the tension within the narrative, as they not only cause immediate danger to the characters but also have lasting emotional repercussions.
The struggle to save Sam from the demon's control is a testament to the show's exploration of themes such as family, loyalty, and the fight against evil. It also delves into the psychological impact of possession, as Sam must grapple with the guilt and trauma of the harm caused while he was under the demon's influence.
In conclusion, the demon that possessed Sam in "Supernatural" is a narrative device used to drive the plot and develop the characters. It is a representation of the darker aspects of the show's universe and serves to challenge the protagonists in both physical and emotional ways. The episode "Born Under a Bad Sign" is a key example of how the show uses supernatural elements to tell compelling stories that resonate with its audience.
read more >>

In 2.14 Born Under a Bad Sign, Sam is possessed by the demon which had previously possessed Meg Masters. While possessed Sam killed Steve Wandell, attacked Jo and shot and beat up Dean. It is initially difficult to exorcise as it has used a spell (signified by a brand on Sam's arm) to bind itself to Sam's body.Apr 15, 2018read more >>