Divine retribution

Divine retribution is the consequence of having incurred penance with a god.

How Retribution occurs

Every time handle_god_time() is called (roughly once every 20 turns if you are neither hasted nor slowed), if you owe penance to at least one god, there is a 1/100 chance that a random god is chosen from those to whom you owe penance and given the opportunity to exact retribution. This means that if you owe penance to more than one god, you will not suffer wrath more frequently, but instead suffer it for a longer time.

Retribution and Good Gods

Good gods will not even contemplate visiting retribution on anyone except the followers of gods they hate - which means that if you abandon a good god, you cannot diminish the penance you owe them except by returning to the fold (whereupon pious actions will atone for your sins) or by turning to the worship of an evil god (and thus unleashing the wrath of your former god).

Overwhelming Retribution

When a god's retribution is unleashed on you, it is possible for it to be "overwhelming". If retribution is potentially overwhelming, there is a chance given by

one_chance_in(5) && (you.experience_level < random2(37))

that you will either (resistibly) be confused for an additional 3-12 turns, or be slowed for an additional 0-19 turns if your outstanding Slowing duration is less than 90 turns.

Penance Reduction

Additionally to any penance reduction arising from the god's retribution action itself, every time you are the subject of divine retribution, your penance owing to that god is reduced by 1d3 points.

If the penance is reduced to zero you get the "<god> seems mollified." message.

Estimating Penance Counter

You can estimate your penance counter by looking at the Favour description on your religion screen (command ^).

Favour	Piety
Godly wrath is upon you!	50+
You've transgressed heavily! Be penitent!	20+
You are under penance.	5+
You should show more discipline.	4 or less

This will only be visible for a god you are currently worshiping, which means that unless you are intentionally incurring penance with your current god, you will probably never see anything but "You should show more discipline." on the ^ screen.

You can also pray at the altar of a god you no longer worship to get an estimate of your penance counter with that god.

Favour	Piety
... wrath is upon you!	50+
... annoyed with you.	20+
... well remembers your sins.	5+
... is ready to forgive your sins.	4 or less