My initial impression is that the Voidsinger Society is very powerful and in some ways makes Holy Sites almost unnecessary unless you are really going for a Religion Victory and need to make lots of religious units but Faith income is so important for a lot of things outside Religion. Old God Monument replaces a building that you were likely going to build in nearly every city with any civ anyway and gives +4 Faith and a relic slot. If you are going wide, this gives lots of Faith to buy a Great Prophet and/or buy Settlers, Builders and Traders during a Monumentality Golden Age, then save up again to eventually buy Cultists and maybe Rock Bands, Naturalists or Great People too. Once you reach Industrial Era and can start buying Cultists you have a quick, reliable and repeatable source of relics and plenty of slots to put them in. This is much easier than trying to get relics from Apostles and needing a wonder or city state to guarantee Martyr promotion because even then, the Apostle has to die in combat to get the relic which means you are depending on the AI to kill your Apostles. The cultist on the other hand gives a relic as soon as they use their last charge with much less effort to get them. If that is not enough already, using those charges helps you to peacefully flip cities to your side. In a wide empire you can very quickly have tons of relics. Found a religion with Reliquaries and you are getting triple Faith and Tourism from each of those relics. You really don't even need to build Holy Sites aside from maybe one to found a religion (or none if you found with Stonehenge) or maybe to get a couple Apostles to finish your religion. If you have any other Faith income from pantheon, city states, Triangular Trade or improvements you really don't need extra Holy Sites. Initially I thought Cultist would not be great at flipping cities because any decent size city would quickly return to full loyalty but after trying it, I was wrong. Send three cultists at any city and you can reduce the city by -30 loyalty per turn for several turns. You can move nearly any city to a Free City and then move your units in to capture the city without ever declaring war and no diplomatic consequences. I suppose you could also use a spy to help but honestly, the city likely will flip before the spy even completes his mission. All of this was without ever using the final Voidsinger promotion that increases the loyalty reduction strength of the cultist even further and just to thrown in another added bonus, the Medieval Era promotion converts some Faith into Science and Culture. Each of the Secret Societies seem good and I haven't had a chance to test the others yet but Voidsingers seem very powerful. What do you think?