I've reached the point in King of Dragon Pass where I want to HeroQuest as often as possible in order to score sacks of phat lewt and mad XP secure the future of my clan, honor the gods, and ensure their blessings for our tribal ambitions.

Sadly, it would seem that the various interchangeable old people that make up my Clan Ring didn't pay attention in Sunday School or thought it was a good idea to not wear their magic underwear or something, because in spite of adhering to the myths perfectly, most of my HeroQuests fail. I have a Trickster on my ring, am dedicating 2 points of magic to Quests and another to Mysteries every Sacred Time, generally attempt each quest with ~10 points of magic in reserve, and one of my allies is usually good for 40 extra worshippers. I always send a worshipper of the relevant god in to impersonate their deity of choice, and yet, I fail nearly every Quest. Hell, in spite of only attempting once per year, half the time I can't even get in to the Godsrealm.

What stats should I be looking for from the people I send on quests? Is it Magic? Combat? Custom?

Is there anything else I can do to improve my success rate?