Most of the Fighters Guild guildhalls in the Alik'r Desert are actually mosques dedicated to Him, which is why vampires take damage while inside. He is also an enemy of most of the Daedric Princes (all except Sheogorath) as well as the Temple of Stendarr and the Cabal (a subfaction of the Mages Guild). He is allied with none, although he does lead the Citadel of Ebonarm (the aforementioned mosques). Holy anvils dedicated to Ebonarm can be found throughout the Iliac Bay region.
For more information, see the lore article.