Sauron built the Temple of Melkor and he taught men to worship and then he damned them all. He bade them sacrifice men on the altar, to kill their own kind in a show of devotion to Melkor, his master.
He smiled to himself. What they didn’t seem to understand was that Melkor wasn’t coming back and it was he, Sauron, who was the lord of darkness now and when they bowed before the bloodied altar to the fallen Vala, they really worshipped him instead.
He was the powerful new god of all evil. He stood to greet his followers.