Mistheism

I don't dispute that gods exist. They do, and that's the problem - they're all a bunch of jerks.

— Canno Godhater, Human Vermin

Mistheism is an human ideology that claim that religions do not exist, but gods do. Churches and temples, rituals and clergy, it's all a puppet-show made by cruel and uncaring gods that play games and abuse their power. It isn't that Mistheists don't believe that gods exist, but that they have a deep and personal dislike for them. The reason for this disdain varies, from the harsh life within the Below to personal interactions to feeling wronged by some misfortune. In human societies, the response to Mistheism is mixed: many believe it isn't worth wasting energy hating on something so far above, many still curse their fate in the Below and blame the gods for it.
Mistheism's spread is scattershot across the Below, and they aren't particularly organized. It's adherents have no clergy, but have agitators who stir up trouble and resentment of the divine where they go. To any clone-kingdom that has made their bet by pledging to obey the gods of the Above, they are beyond a nuisance and hunted.
To the gods that take note of them, Mistheists are amusing toys and pawns, so easily riled up yet so unpredictable. More than a few Mistheist breachers owe their survival to gods of the Above who watch their adventures with great interest and do what they can both to prolong it, and make it miserable. If they knew, those breachers would probably slit their own throats just to spite those who watch them.

Breachers

Mistheism is overrepresented in the ranks of the Breachers, many who seek to defy their exile to the Below out of sheer spite to the gods that did so. Gods have been killed before, and they can be killed again. When no divinity is left, all can be equal to the now dead gods.
Breacher of Heaven