Mr Wagner was one of Mr Finch's Krillitanes who took over the Deffry Vale High School to solve the Skasis Paradigm and become "gods". All the Krillitanes were destroyed when K9 blew up a can of their oil. (TV: School Reunion)
He differed from the others in that his true Krillitane form was grey. He was the only one known to be so.