United Creed is a organization who worships demon lord and formed a religion to follow him.
It is the local cathedral. Since the Demon Lord left the ancient world, the Demon Lord had become a convenient symbol for politicians everywhere. They’d created a religion with it as the major deity—which he bet had been an attempt to incite the public in an act of demagoguery. The sect was called the United Creed. Its namesake came from demon lord's unification of the entire world