They say that your life flashes before your eyes before you die... devotees of THIS cult go out of their way to make sure that it happens! For this is not just a death cult, they are enthusiastic gatherers of knowledge even (or is that especially) from those who don't want to share it, and they also provide civic services: they run libraries and gaols.
It's unlikely many characters will want to join this cult, but they can provide an intriguing, useful and scary bunch to have around. They are quite happy to hire out to any lord or state that needs a gaol but doesn't particularly want to go to the trouble of running one, and even track down anyone who has the temerity to escape. As unlike many death cults they are as happy to embrace death as to inflict it on others, they make scary opponents - quite fearless in battle and very determined.
Leadership is loose, they claim to get directions from the deity through visions during near-death experiences... and as they are not afraid to die, they are quite happy to seek divine inspiration via this method. As gaolers they are quite brutal, and some warlords have been known to employ them to find things out from their captives as well as keep them imprisoned.
Once the nature of the cult has been described, along with different 'levels' from a mad old woman living in a cave to a territory-wide state sponsored subjugation run by devotees, you get sample NPCs and a list of their practices to add flavour to their presence. There are several adventure hooks to provide ideas on how to get them involved in your campaign. There's also a rough plan of a typical cult base, an underground prison/library built into a mountain behind a waterfall - a typical location for them.
Overall, there are a lot of good ideas if you are looking for inspiration, a well-developed (if quite nasty!) cult to incorporate into your campaign world. In a perverted sort of way, their teachings hang together, enough to make them sound as if they could exist within your alternate reality. Being a generic resource, you will have to do some work to fit them into your chosen ruleset - but provided you know your way around the game mechanics, there is plenty of detail here to help you to utilise them.