From publisher blurb:
Microlite74 Light vs Dark (formerly titled Microlite74 Special Version I) is designed for a campaign world with only two deities (a Lord of Light (order) and a Lord of Darkness (chaos) who oppose each other. Magic is both common and rare in this campaign world in that about 25% of the population have the ability to use Minor Magic at will (including all characters and NPCs with a class level), but arcane magic is otherwise limited to long, complex, and costly rituals. Clerics have limited spell-like abilities called prayers. True magic Items are almost non-existent. What true magic items do exist are created by the GM as needed and are always one-of-a-kind. Magic items created by binding spirits to material items are more common.
The proprietary setting these rules were designed for was centered around a large decadent empire which which was starting to fall apart at the seams while its borderlands were breaking away or were being overrun by subhumans and monsters. The central portions of the empire were ignoring the problems. The Church of Light was aware of the problems but its influence on the imperial government had been reduced by scandal after scandal. In the borderlands, however, the Church of Light was often the only institution able to see beyond local issues. The campaign world was early renaissance, at least in the central parts of the empire, but hand guns and long guns were never invented. However, the Microlite74 Light vs Dark rules will work fine for any setting with two powerful opposing deities and weak, but fairly common magic.