Griffith Dragonlake said:
Any particular reason why the cult of Apollo was not subsumed by the cult of Sol Invictus? Was there any Greco-Egyptian syncreticism? Such as Harpocrates and Serapis? And did the Romans invent a cult of Mithras which bore little reationship to Persian Mithraism?
All in all, way cool.
Mostly because the gods are very real here; true deific syncretism is rare in this world, and only happens when one god kills another and "takes his stuff."
Another reason is the different history of the empire... here are my notes on the founding of the Roman Olympian Faith. They've neither been edited for grammar nor for content, so there may be odd bits here and there...
The Roman Church is an outgrowth of the attempt of the Roman Empire to unite its disparate people under one faith, in order to strengthen the Empire. The Emperor of Rome had ever held the title Pontifex Maximus ("Ultimate High Priest"), as the supreme mortal leader of the Roman Pantheon. However, until the reign of Antonius Pius (3138-3161 AA) it had been a mostly hollow title in fact, with few powers of its own, as the Pontifex Flamen ("Grand High Priests") of each temple held more power within their own temples.
Then, in 3140 AA, Antonius conferred the title of Pontifex Rex ("King Priest") upon Marcus Annius Verus, the extremely capable brother-in-law of his heir, Lucius Ceionius Commodus. [History went on to show that Marcus would have been a far better Emperor than his brother-in-law, also named Lucius Ceionius Commodus, but that is another story]. Marcus, a stoic philosopher, began the process of uniting the various Roman temples into one organization, under his own rule. It was a hard process, but the nascent united church was allowed to grow for 20 years in the fruitful and peaceful period of Antoinine rule, and then the additional 20 years that Marcus survived after the death of Antonius. By 3180 AA the church was well founded, with the title of Pontifex Rex being second only to that of Imperator.
The Roman Empire was dissolved in 3315 AA at the Treaty of Tingi. The regions that had been in rebellion, supported by the Atlantlan-Phoenician League, returned to self-rule, while the highly Romanized regions (Italia, Britannia, Gallia, Aquitania, Iberia, Numidia, and Dalmatia) were ruled by a Romanized elite. The Roman Church remained to unite the disparate successor states during this period, especially under the long rule of Pontifex Rex Constantinus Pius Britannicus Invictis (3307-3337 AA). For decades the priests and bishops of the Roman church were able to keep the various successor states united against the invading hordes from the east. Then, in 3364 AA, Zeus/Jupiter and Hades/Pluto were assassinated in the opening salvo of a major war among the Pantheons of Aerth (a war which continues to a lesser extent to the present day, 4130 AA).
The Great War of the Heavens lasted more than 100 years, and was reflected in the chaos and catastrophe that occurred in the mortal world below. The death of Zeus/Jupiter left the throne of Olympus wide open. Ares/Mars, Apollo, and Heracles/Hercules all vied for the throne in the first civil war among the Olympians since the time of the Titans. In the end, Ares/Mars was slain, and Apollo relinquished Olympus to Heracles/Hercules and decided to rule from on high, one-upping Hercules from the skies above. The death of Ares/Mars was not as big a deal as it sounded, since Hera/Juno, his mother, had taken over the Underworld after her assassination of Hades/Pluto, and she immediately resurrected him as her herald and strongman. The rest of the Olympian gods chose sides or otherwise remained neutral.
The Great Schism, as the resultant status quo was called, resulted in a split church among the mortals below. The eastern, Greek territories mostly proclaimed for Heracles, their favorite son, while the western Latin territories proclaimed for Apollo. No one region ever proclaimed for Ares/Mars; he and his mother were relegated to cultic status, or became secondary players in the new Roman and Greek pantheons. From the first, the eastern Patriarchs refused to recognize the authority of the Pontifex Rex, and instead chose their own Episcopus Maximus ("Ultimate Bishop", really little more than first among equals). In time, the Patriarchate of Athens came to be the chosen location of the Episcopus Maximus, due to location, wealth, and tradition (plus, it kept the Episcopus out from under foot of the Emperor of Byzantium). If the various states had not been more concerned with the invading barbarian tribes, it might well have come down to a full-out religious war on earth.
However, the Roman and Greek peoples were more concerned with the invading Germanic and Turkic peoples at the time. The now-disunited Roman states were invaded by Germans while the Greek states were able, for a time, to unite against the invaders and push them into the staggering Roman states. By 3500 AA, the Roman states were almost obliterated, ruled by pagan Germanic chiefs and kings. The only surviving marginally Romanized regions were Gallia and Aquitania (where the Franks had adopted the Roman faith); the north-eastern corner of Iberia (held by the native Romanized Basques); and a few Romanized hold-outs in Britannia (attempts to establish a presence among the pagans of Hibernia in the early 35th century failed). All other areas where the Roman Church once held sway were under the control of Germanic pagans, including Rome itself! However, the Germans never tried to convert their subjects to their own faith, and in time, they themselves converted, and the Roman Church survived.
The Greek or Byzantine Empire (founded in 3476 AA with the conquest of Dalmatia) was, in addition to holding the core Greek states, able to conquer Dalmatia, Numidia, Galatia, Armenia, and, for a brief period, a portion of Iberia, Italia, and even Hasur. Named after the village atop which the city was built, the Byzantine Empire, due to its highly regionalist nature, never further united its church. During this period the weakness of the Roman Pontifex Rex (who did not even rule his own city let alone an empire) combined with the regionalist nature of the Greeks to further ingrain independence within the Greek Church's structure. By the late 37th century, the Germanic tribes that had conquered the Roman kingdoms had all converted to the Roman faith, and the Greek Empire seemed to have finally gotten a handle on ruling over a large region. Then, in the mid-37th century, another round of invasions began.
From the east came the Yarban hordes, united of the banner of the Babylonian sun god Shamash, while from the west and the south the Atlantlans were able to force one last attempt to regain an empire. The Yarbans extinguished the Second Persian Empire, decimated the Greek provinces of the Levant, and even ran over and conquered Lower and Middle Aegypt, pouring out into the wastes of Lybbos and Keshu. Likewise, at the same time, the Atlantlans flooded in on the coasts of Iberia and Numidia. The Atlantlans conquered the Iberian Peninsula as far as the Pyrenees, and even took a small strip of southern Aquitania. In Numidia they conquered all the territories held by the Greeks with the assistance of the Phoenicians, who retook Carthage. Byzantium was sacked by a Yarban invasion in 3680 AA, and the Greek Empire fell into chaos; the northeastern territories were lost in short order, and the empire itself was nearly lost (the northern Dalmatian provinces even falling to a minor horde from the northern steppes, the Avars). Eventually, the new emperor was able to offer a counter-offensive. The Atlantlans were soundly repulsed from the west in 3737 AA by Neustrian Romanized-Frank forces. Finally, some peace was gained on the Aeropan fronts when the two invaders decided to start fighting each other over control of the Mare Phoenicium and the Phoenician states (3747 AA).
The two churches both grew stronger during this period and in the centuries following, as their constituents clung to their gods in this time of war and catastrophe. The faithful in the pagan lands were, surprisingly, allowed to keep their own faiths (though they were invariably heavily taxed for doing so and usually oppressed, especially so in the Atlantlan territories). The Roman Church operated to coordinate regional defenses and cooperation, while the various Patriarchs of the Greek Church worked together with the Byzantine Emperor on the same. By the beginning of the 39th century their efforts had taken root. In the west, the Kingdom of Galicia had begun the re-conquest of the Iberian Peninsula, a task made easier with the final collapse of the continental portion of the Atlantlan Empire in 3793 AA. The greatest Roman success was the founding of the Frankish Empire in 3800 AA. The founding of the empire was a fantastic coup on the part of the Pontifex Rex; with it, and with his crowning of the Emperor, he assured the strengthening of the bonds between the temporal rulers and the spiritual leaders in the west.
Unfortunately, it was a temporary victory of sorts, as the empire collapsed after less than 100 years, due to political infighting and the recalcitrance of the German and Slavic subjects of the empire to convert to the Roman faith. The only successful conversions in period were a fair percentage of the Helvetian, Burgundian, and Bavarian Germans, with some inroads with their Alemannian and Saxon brethren. However, the re-insertion of the Pontifex Rex into the direct temporal political scheme dramatically altered the nature of Roman civilization.