Conquest of Elysium 3 is an old school fantasy strategy game. You explore your surroundings conquer locations that provides the resources you need. Resources needed vary much depending on what character you are, e.g. the high priestess need places where she can gather human sacrifices, the baron needs places where tax can be collected and where iron can be mined. These resources can then be used for magic rituals and troop recruitments. The main differentiator for this game is the amount of features and special abilities that can be used.
The game can be played on Windows, Linux (x86 and raspberry pi) and Mac OSX (intel and powerpc).
The demonologist can choose how generous he should be when sacrificing humans to the demons. Smaller sacrifices means increased risk of the demon attacking instead of obeying. He can also summon demons without making any sacrifice resulting in an automatic battle. This is usually a bad idea, but at least demons often have magic weapons that you can take if you win.