From the Chaosium website:
The First Cthulhu Invictus Companion
In suus domus procul R’lyeh mortuus Cthulhu exspecto somnium
– Graffiti found scrawled throughout Pompeii following an earthquake, August 20th, 79AD
The translation of the above graffiti should be well known to most fans of the Cthulhu Mythos. It is “In his house at R’lyeh, dead Cthulhu waits dreaming”. For a time the Roman Empire stretched across most of the “known world” uniting various peoples under its rule. Cultures met, clashed, were conquered and changed one another in the processes. Information traveled along Roman roads along with goods and troops, spreading knowledge and enlightenment throughout the empire. Rome, for some, meant civilization, order and justice. For others it meant enslavement, oppression and occupation. It was the crest of history’s tide, and when it was gone darkness and chaos reigned for nearly a thousand years. But for now the Roman Empire was a light that kept the dark ages at bay, but with every light there are always shadows.
Amid sprawling cities and frontier garrisons, from peaceful country villas to newly constructed catacombs the forces of the Cthulhu Mythos lurked, and thrived. As the Empire spread across the land the Mythos infected it, like an illness, using Rome’s uniting light to spread its own darkness. Isolated covens and cabals of dozens soon became well-organized cults of hundreds, spread across vast stretches of the empire. The accumulated knowledge of the ages was examined, connections made and puzzles solved, sometimes to humanity’s misfortune. The forces of the mythos quickly learned that civilization was as easy to hide in as wastelands but with much more abundant prey.
However, in every age there are always a few who learn the truth. A small handful of people always seem to discover that all is not as it seems and slowly pull back the veil of what mankind tells itself is reality. They see, they learn, and usually they die; but not always. Some take up arms, be it blades or arcane magic, and choose to stand against these shadows. They become mankind’s defenders, fighting to protect others from the truth while moving to rid the world of these shadows of evil. In every age there are always a few such people, it was no different in the time of the Roman Empire. Here are a few of their stories. Welcome to Malum Umbra, Shadows of Evil, The First Cthulhu Invictus Companion.