This is the monotheistic religion for a world with magic, and had many deities at one time. It now has three (and a half) religions associated with this one deity.
The Messenger claimed to be the (spiritual) Son of the Primal Deity, call BA’AN (or Primal One). This primal deity created the universe and all the other lesser Gods. Those deities were supposed to run the place while he was gone finishing things up. These lesser Gods took the credit for creating the universe and being true powers, rather than simply administrating things for the Primal One. Upon his return to the world, He (the Primal One) took the reigns from those lesser gods and forbade their worship. He sent his (spiritual) son to inform the people of this change and his Avatars (Angels) to inform the lesser gods. Those lesser Gods that did not rejoin the ranks of the Avatars were destroyed.
Many people resisted the Messenger and his new faith. They were entrenched in the existing order. Yet, all of a sudden, there was no clerical power. The Messenger, and his anointed followers, had clerical abilities.
People know that the lesser Gods were defeated as their clerics could no longer draw upon their power (i.e. no clerical spells). Thus people began to acknowledge that the Message was true.
The Messenger’s Church was built upon the ruins of the lesser churches. The religion has a Judeo Christian feel (centralist with focus upon good works/ life), except that the Avatars/ Angels are given special worship, much like Catholic Saints. The Messenger’s Church is the only source of healing (magical or otherwise), spiritual protection (spells vs demons, magic, and Evil), and wisdom. The Paladins of the church, tend to be witch hunters- those that hunt witches those that use magic beyond mortal control (i.e. infernal magics from the Outsider deities). They also protect priests who go out to spread the word of the Messenger.