Last time I ran 3.5/pathfinder (when the later had just came out).
It was a 1000 years since the humans lost the war. "1000 years ago it was a time for heros.... and 1000 years ago those hero's failed. Now it is a time for hero's again, and if they once again fail then even the trace that remains will be extinguished."
Basically humanity has been reduced to a food source.
When I say humanity i mean dwarvemantiy, elfvanity etc. All people were mudbloods, except the PCs who were throwbacks.
Kept in fenced slums, by a bestial race called the Cron.
There was no magic, all knowledge was lost, all items destroyed.
To make up for this, because dnd assumes a particular wealth curve.
I gave everyone the benefits of Vow of Poverty, but without the restrictions.
They could have all the items that wanted,
but the best items that existed were Masterwork.
The in game logic behind the vow of poverty benefits in this case, is not that they are blessed for there faith,
(Indeed what is there to believe in in this world, no doubt the Cron killed and ate our gods with the last of the priests.)
But that if you are still alive then you are one tough dude, especially if you manage to get to a level where the benefits stack up.
The rough thing that vow of poverty was is a table listing benifits you get at certain levels.
It was things like: AC bonuses, extra feats, +2 bonus to your choice of stat, damage reduction.
I can't remember which 3.5 book Vow of Povery is from. I think book of exhalted deads of some thing like that.