User blog comment:Madman97/The Peryite Theory/@comment-9062114-20140730234553/@comment-11345660-20140731000239

Malacath is not originally a Daedra, but Trinimac, who was tricked by Boethia and then devoured by him and turned into Malacath. Because he was not originally a Daedra, as recorded in the book Changed Ones, and it is implied that the Daedra do not consider him a Prince because of his Aedric Origins, and Sheogorath says that Jyggalag is less popular than Malacath at parties, "And Malacath IS NOT popular at parties!" A suggestion that invokes the sense the other Princes alienate him. Not outright mistreatment, yes, but isolation.