Units with the heretic trait have a 20% * heretic level chance each turn to reduce the dominion strength in the province they are in by 1.

Example: A heretic 3 in a province has a 60% chance to reduce dominion strength by 1, with 3 heretic 2 commander in a province there are 2 40% chances of dominions strength being reduced.

A heretic in a province with 0 dominion strength has no effect.