The game advice listed during game startup talks about being able to get quests from the "Temple of Light" (I mis-named it accidentally in the topic header, it is Temple of Light, not Temple of the White Light).

I have never seen a Temple of Light. How do I build/access it?

They are found sometimes in Provinces by Exlporing it fully. It's not in all provinces so sometimes it's just getting lucky.

Sometimes you don't even need to explore.
You can take their quest like with crystal in your own castle.

Their quests mostly about killing undeads or demons, and often out of depth.
Some nearly impossible to complete, like killing vampires or devils (almost impossible to meet in early campaign).

I very rarely manage to complete those quests, not due to lack of power but due to lack of enemies to kill.
They usually ask me to kill some pretty rare monster.
When I do, its just normal quest rewards.

@Gremlion: Is there a karma penalty (or another consequence) for conquering a temple of light?