The Cult practiced the ritualistic teachings of the legendary Hermes Trismegistus, who may have been a mortal mage or even the god Hermes himself. Their magic was worked in concert, with hundreds of priests, acolytes and initiated magi across several cities, and accordingly took a great deal of time. While not one of the most powerful religious cults of the Empire, at its height, even a number of senators were counted among them. As Rome expanded the bounds of its empire, the cult came into conflict with "barbarian" mages on the outskirts of the empire, such as the predecessors of the Verbena. While the magic of the Mercurists was entirely ritualistic and had more in common with Linear magic than Awakened arts, in the second century BCE the magician Plentarch of Pompeii codified numerous rituals into a catalogue of thirty-eight proto-Spells that were going to be used by its standard members. Impressive for its time, the Cult accepted converts from every part of the Empire and tried to incorporate foreign traditions to the best of their abilities.
It's thought by some scholars that the spells the Cult cast were essential in the long-lasting integrity of the Roman Empire.
Since the Cult of Mercury required so many dedicated priests to cast even a single spell, as well as broad financial support for the ritual components, it lost much of its power as Rome decayed. The cult fragmented as different groups of priests chose different sides in the civil wars, and by A.D. 300, most of its stronger spells could no longer be cast, because of the lack of cooperating priests. When Christianity became the official state religion, the Cult of Mercury was forced to abandon its temples and had to practice its craft in secret. This diminishing of the Cult and its ability to cast spells may have weakened the structure of the Empire, which caused a vicious cycle of collapse.
The cult finally disintegrated after the fall of the Western Roman Empire, with individual magi being able to perform only minor magicks unless they worked in concert with others. Unfortunately, individual wizards were paranoid about working together, and mostly worked in seclusion. They had adapted their highly-regimented magics to be able to be used on an individual basis, but it was still fairly weak, a far cry from the height of the Cult.
The full teachings were rediscovered by the mage Bonisagus centuries later in his search for a universal theory of magic. Bonisagus went on to spread this lost knowledge among any and all European mages who would listen; the fellowship that emerged from this shared knowledge became the backbone of the Order of Hermes. Of the 12 founding magi of the Order of Hermes, ten were descended from the Roman priests of Mercury.
A small revivalist force of Sorcerers has tried to revitalize the Cult, researching its magic to the best of their abilities.
- The symbol of the Cult of Mercury was a roman Aquila grasping a caduceus within its talons.