The Apocrypha out of the BoU as posted on Shadekeep's website I think is enlightening to read and a worthwhile supplement. As such it adds a good deal to the priestly figure's stock in trade.
Pertaining to séance contacts and rites of passage with the afterlife, I once made up a solo adventure designed for player figures who'd been lost in the course of play, using the free Dark City Games derivative ruleset. I post it here:
http://playhob.com/Case/rehG5.html