It's not fully fleshed out to be perfectly honest with you, but I can share the details I have.

Communion with the rift via accessing its realms is considered a gift from the 'eternal' that dwells within. 

The Endless ones are you the adventurers. So long as your likeness is stored in the Blooded infinity shards, you can be reborn within a rift and returned from 'death' itself. 

There is an 'eternal' spirit that the worshippers believe resides within the Infinity Diamond itself that controls, shapes, creates, and transports its denizens to and from their destinations. It is this being that spreads the very corruption you will find on the otherwise pristine rifts you venture through. 

Their symbol is an ever burning candle.