Military action
Emperor Diocletian declares war on the Illuminati.
Emperor Diocletian noticed a problem. Children were disappearing. And everyone of them was a mage. The empire was in dire straights as it was, he didn't need a lack of mages hamstringing him. A short investigation later and an agent of the Illuminati was kneeling before him. An extremist sect of a cult that was at it's core unfriendly to Rome. He wondered briefly, if he could eliminate this one sect of lunatics, could he bring the entire cult to heel? His son-in-law Galerius, advised against it. This was no time for half measures. And so the persecutions began. To the south, in the middle of their desert stronghold, The Illuminati saw the pagans declare war on their people. Thousands being slaughtered because they dared to hope for a forgiving god. If the Emperor wanted war, then war they would bring. The records for The Secret War are for the most part, sealed. Hence the name. What is known, is that it was played out on a couple different fronts. One, was the assassin front. This is commonly believed to the origins of the order known as the Assassins, long be they were hijacked by the Nizari Ismailis. They battled in alleys, rooftops, and on one occasion, Diocletian's bed chambers. Nobody was safe, even the Rex Sanctorum was brought low on the steps of the Fortress. Many tactics the Illuminati would come to rely on were developed here. The other front, was the religious. At first, Rome held the advantage. They had history and an imperial edict on their side. The state religion would hold. But, the Illuminati was used to working in secret. Ichthys began cropping up. Masses held after dark. The Illuminati scored victory after victory. Rome's hold on the people's soul was broken. The Empire already broken in two, succumbed to the holy onslaught. In the west, Maxentius took the throne and called for tolerance. In the east, Galerius continued the fight for another five years, before surrendering. Rome had failed completely. The Illuminati had laid the foundation for Constantine's rise in a few years and there were more Christians than their had been before the war. Rome tipped further into irrelevancy. The empire's time was coming to an end.