When Elizabeth Tudor succeeded to the throne in 1558, she found herself under assault from all sides, paying for her father's arrogant machinations, and the weakened barrier between worlds his split with Rome had caused.
As magic and creatures of the supernatural proliferate throughout the land, the Queen passed an Act Against Conjurations, Enchantments and Witchcrafts, making the punishment for acts of magic more severe than others, but in many cases drawing the line before a death sentence. In 1564, John Dee and Francis Walsingham convinced the Queen to pass an amendment to the Act — The Dee Sanction — permitting the practice of magic in defence of the realm.
You are an Agent of Dee; not out of choice, but out of some twisted sense of self-preservation. Somewhere between conscription and penance, you work for Walsingham and Dee to make amends, with a faint hope that you can use your talents to earn your pardon and absolution.
You can see the light at the end of the tunnel. If only you can outrun the shadows of your past and the horrors of the present…
This is The Dee Sanction.
I think alternate history games make for fertile gaming ground because you can access a lot of reading material around the subject (or in the case of Twilight 2000, speculation and adjacent material) without needing to adhere to a canon road map of campaign development. In a historical game, like The Dee Sanction, that might mean that people live or die at odds with the true timeline, while factions, reimagined or completely fabricated, clash and scheme in pursuits of end games that never existed.
You can create whole new campaigns for power, plots to dethrone the Queen, or quests to engage new allies or acquire new weapons; but, when the ideas don't flow, the library has hundreds of "sourcebooks" to check out in pursuits of something new.