I am hoping to have a monarchy that is revealed to be under the control of the priesthood. The idea is that the monarch-to-be undergoes a secret ritual before ascending the throne. That the ritual ostensibly turns the monarch into a direct conduit to the gods is used as an explanation for his or her change in personality after the ritual. I want the monarch to completely be the puppet of the priesthood. Ideally he or she should have minimal willpower of his or her own, or be extremely compliant and highly susceptible to suggestion and manipulation. Ideally, I would like the monarch to have most of their personality eliminated entirely, but this is not necessary. Basically, I'd like to turn a human being into as much of a mindless robot as possible, though they should still be able to act and think independently, if they encounter an unexpected situation that their keepers haven't prepared them for. The most important point is that I need a methodology that could work regardless of the sex of the individual, although I would be open to the process being more effective on one particular sex, as I could theoretically use that to help explain the development of gender roles in my society. The process need not be reversible. I'd also need to know, if course, what other side effects would likely occur as a result.
My research on this point has been minimal, but so far my focus has been mainly on hormone inhibition. I remember watching something recently about transferring human consciousness to machines and one of the people interviewed cautioned that, since we could not transfer hormones, it is quite possible that such a process could preserve our memories and consciousness, but destroy our personalities. I'm finding most of what I have seen to be too scientific for me to really understand, simplified to the point where I feel like I run the risk of misunderstanding completely how the hormones in question actually work, or focusing exclusively on reproductive hormones. The setting hasn't been established yet, but we'll say futuristic earth, advanced theoretical technology permitted. I would like to avoid achieving this through any use of magic, if possible, though I could possibly use some to handwave minor details if necessary. I'd also like to avoid too much psychological manipulation. Chemicals, medications, surgery, and so on are really what I had been hoping to use.
Thanks for any suggestion and help you can offer :)