Help us catch the undocumented--game features, I mean. Post anything that isn't adequately detailed (in-game, not forum or wiki). Not neccesarily to answer you questions here, but to get the info in Cid's tips or Game features pedia.

The effects of the Demon and Undead promotion.
Immunity to disease, the inability to profit from a whole bunch of spells, inability to keep the people in a city content. Anything else?