Arthur

Arthur is introduced to the guests as the 'Head of Staff' by Joey when the guests first arrive. In Episode 9 he is revealed to be working with the evil of the house, tagging along with Sarah and Marvin. He is eventually slain by his own brother.

Backstory
Months before moving into the main mansion, Arthur once lived in a home with his ex-wife. He states, 'I was a confidence man and I played games with people's lives'. -Arthur (Episode 10) In this home, on he and his wife's anniversary he made tea for her. Hiding the poison, he added it to his wife's tea cup. Once he handed her the tea cup, she smiled and drank it, poisoning her. She fell dead into the floor, which he then left the house, leaving the wedding ring. He says he had grown tired of playing the same game every time, he wanted more. The Devil then came calling to Arthur, leading him to the house. He convinced the evil within the house that he was it's servant. After officially becoming the home's butler, he invited his brother over to help clean up. Once his brother arrived, he imprisoned him a closet in the Back Basement for no one to know about. Afterwards, he hired Sarah and Marvin, who were also working with the evil.

An Invitation (Episode 1)
Arthur is first introduced in Episode 1, when he walks down the stairs to open the car doors for the guests. Joey introduces Arthur along with the other staff to the guests. Later on at dinner, Arthur brings a telegram note to Shane, then walks off.