Anno Domini 1666 is a game set in a fictional world. However, its functioning is much simpler to understand than most fantasy universes. There are two key points to consider.

Firstly, it is heavily rooted in history. If something is not historically accurate, there is likely an intentional reason behind it, which is more or less significant to the storyline. The dating of costumes and equipment is not strictly confined to 1666, but deviations are minor. The phrase best describes Other deviations from history: “It probably didn’t happen, but people could believe it.” This includes phenomena like vampirism and lycanthropy.

The second important aspect is that our world is fundamentally biblical. It was created by God and is plagued by the influences of rebellious beings called demons, led by Lucifer. Their influence on the world is what we term magic. This means that behind every spell and magical trick, there is a demon, who, though invisible, moves objects (telekinesis), ignites fires, or shares knowledge (divination).