Civilization A has a fixed population; so they need armies from outside sources to protect themselves. After many years of reign over a nearby civilization (Civilization B) to supply armies for A, several uprisings have cut into the population of A. A therefore decides to impregnate B with a religion where certain "signs" or "prophecies" would make B act predictably if A forced these signs. Control from A was covertly maintained by this religious impregnation and drugging the city's water supply.
What drug would A use to force chemical dependency on B; so they don't just leave B?
- Must be water miscible
- Must induce mild torpor
- Must induce mild euphoria
- Must be effective at low concentrations
- Must maintain effectiveness after repeat exposure
Answers will be evaluated by which drug has the largest effect while going unnoticed by the user. (e.g. drugs with few side-effects will be favorable to drugs with severe or many side-effects)
Bonus points for drugs which include other qualities to help make users impressionable.
*mind altering parasites are also viable