Flesh and Steel
There are four Pantheons of Gods in the world. Each of the Pantheons come from the same general origins, and the worshipers of the Gods within the same Pantheon tend to have peaceable relations, but you will never find a peaceful combination of temples of different Pantheons in the same settlement.
The Old Gods went by many names across the disparate people of the world, and never chose to reveal the true names which they referred to each other by. As such they tend to be called by their title along with their local name.
There was a time when the Old Gods were worshipped by most of the people of the Empire, but a few hundred years ago Saint Invictus declared a pogrom against all who were not of the faith. The Temples of the Old Gods suffered the most in the ensuing decades, and now few of their holy places remain. Those of the faith of the Old Gods have to keep their beliefs hidden and worship at one a secret shrine; though a few priests of the Church of the Saints are actually heretics who secretly minister to those who still carry the Old Faith.
Some scholars among the Church of the Saints argue against the divinity of the Fata Councillium, but few other words accurately describe the power of these beings. Their followers are not organized in any discernible way, and there is as much fighting between the followers within the Pantheon as there are fights with those of other faiths.
One of the qualities that is common among all of the Fata Concillium is that their prayers are not supplications to a higher power, but more an act of trade between the supplicant and the God. And the Fata Concillium have been known to act on behalf of people who are not faithful to them because it suits their whim, or some grand purpose of which mortals are not aware.
It was this capricious nature that encouraged the Church of the Saints to attempt to purge the faith, which has met with mixed success. The faith has only ever been active in remote rural areas, and for all of the work done it still remains a strong force in the lives of many common folk.
Currently the youngest and most dominant faith of the world. It started as a persecuted cult which was eventually adopted by Emperor of Augustus Maximus, who claimed divine vision that by converting he would invincible. He changed his name to Invictus Sol, and at the end of his reign ascended to become one of the saints that is now worshipped by the faith. There are over five dozen divine saints, but only eight are widely worshipped.
Even though the power of the Empire has waned the reach of the faith it spread has not. The precepts of the Church of the Saints, which is very human-centric and anti-arcane magic continues to find converts to this day.
There are some thing older than even what are referred to as the Old Gods… things that even the Gods speak of in hushed and worried tones. They are the Primordials. Only the most deranged and corrupt souls seek favors from these beings of madness and destruction… though it is rumored that some communities terrible tributes to the Primordials out fear and necessity.
The Primordials are thought to have existed when the Earth was still young, and their worshipers claim their deities were the midwives of its birth… but little lore exists to prove that this is little more than the pathetic boasts of condemned cultists. What is known is that the Primordials revel in destruction and chaos, and reward their followers for inflicting mayhem upon civilization.