I have an idea for a story and doing some research.
Were there any groups and/or organizations that were followers of Hades, who acted in his name?
Were there any tyrants, oppressors, or evil rulers in Greece?
What's the oldest known secret organization and how far is it from Ancient Greece? Are there Secret Organizations that have supposed or confirmed connections to others?
Were the Persians considered the Greeks mortal enemies? What did they think of the Gods the Greeks believed in? Did they have any prominent rulers or figures that hated Greece? That would be considered evil tyrants? Did they have any connections to secret organizations?
Hi there - we're happy to approve your question related to your creative project, and we are happy for people to answer. However, we should warn you that many flairs have become reluctant to answer questions for aspiring novelists and the like, based on past experience: some people working on creative projects have a tendency to try to pump historians for trivia while ignoring the bigger points they were making, while others have a tendency to argue with historians when the historical reality does not line up with what's needed for a particular scene or characterization. Please respect the answers of people who have generously given you their time, even if it's not always what you want to hear.
Additionally, as amazing as our flair panel is, we should also point out that /r/AskHistorians is not a professional historical consultation service. If you're asking a question here because you need vital research for a future commercial product such as a historical novel, you may be better off engaging a historical consultant at a fair hourly rate to answer these questions for you. We don't know what the going rate for consultancy work would be in your locality, but it may be worth looking into that if you have in-depth or highly plot-reliant questions for this project. Some /r/AskHistorians flairs could be receptive to working as a consultant in this way. However, if you wish for a flair here to do this work for you, you will need to organize this with them yourselves.