As always, the public domain contains some of the greatest stuff imaginable to help you design your roleplaying game campaign. Here's a pamphlet about one of the most interesting and conflict-laden periods in history, The Opium Trade, including a sketch of its history, extent, effects, etc., as carried on in India and China by Nathan Allen.
The opium issue was highly complicated - central governments either turned a blind eye to it, or took abortive efforts to stamp the opium trade out. Covertly, efforts were made by various parties to enhance the opium trade for reasons of international intrigue, or naked greed. Unintended consequences both political and social spread across the world during the 19th century as a result of this very complicated drug war.
This pamphlet is a revised edition of what Allen (a medical doctor) had originally written in 1850. It is interesting because it contains both medical and financial descriptions of the opium trade, while containing the paternalistic and racist attitudes of concerned English citizens of the time.
Any Victorian-era game can take on a new dimension when we look at the opium wars, one of the longest-standing and most complicated drug wars ever to be conducted.