The following information was taken from the Red Devil page on the Scream Queens Wiki.

The Red Devil is the main villain in the first season of Scream Queens. The Red Devil was the mascot of Wallace University, until it was replaced by Coney, as the costume was stolen by the killer. It is revealed in Chainsaw that there are at least two killers, taking orders from the planner Gigi Caldwell. The first Red Devil to be revealed is Boone Clemens in Ghost Stories, who is the main killer of the team, and the second is Hester Ulrich in The Final Girl(s), who is the brains and mastermind of the team. It is also revealed that Pete Martínez would wear the costume and assist in the killings. Basically, it is a "Red-Devil-Team" formed by Hester, Boone, Pete and Gigi.