The religion believes in reincarnation, but that you will be reborn in the past. People of today are those re-born of tomorrow, with some discarded as trash. The most pure will be eventually reborn in the mythical paradise-like past, where people lived for hundreds, or maybe even thousands of years.
This goes nicely with beliefs into foresight (you know a little about the future because you have been there), but also to many complaints of how things are going always from bad to worse.
Finally got the idea for an orcish currency:
A cold-hammered piece of raw iron, resembling some kind of a dagger. The Dagger is easy to carry, hard to forge, may be used as a crude weapon in case of emergency AND the iron being a valuable resource... may be used directly for weapon-making. May be carried openly on the belt of a mighty Orc. A new insult: 'to beat someone with someones money' . Self-explanatory.
This really comes from an ancient Chinese novel. Imagine during the PCs' travels, they come to a place where the gender roles are completely reversed. What adventures will the PCs encounter in such a place?