Something very interesting I came across when reading one of the Pocket Guide to the Empire books.

"Traditionally, the Orcs have worshiped [http://www.uesp.net/wiki/UESPWiki:Spelling#Quotes] the Daedra Malacath (Mauloch) as their patron deity. Gortwog, however, has established a new priesthood devoted to the worship of Trinimac, the ancient hero of the Orcs, who legend has it was devoured by Boethia and became the Daedra Malacath. The Orc King's belief that Trinimac still lives and that Malacath is a separate entity, a demon whose aim was to keep the Orsimer pariah folk forever, is the official position of the shaman priests of Orsinium. A minority of traditionalists within the territory, and the majority of Orcs without, view this as heresy. There is fear even among those who support Gortwog and Orsinium that turning their back on the Daedric Prince of the Bloody Oath is a dangerous policy indeed."

It's a very interesting concept, though I do think Malacath genuinely cares about the Orcs, as shown in 16 Accords of Madness which mentions how he suffered when the Mad God caused the death of one of his children.