The Book of the Righteous (d20 System, Green Ronin Publishing)

A massive and richly detailed sourcebook of deities, religions, and mythic lore, The Book of the Righteous is widely regarded as one of the finest third-party supplements of the d20 era. With deep worldbuilding and ready-to-use material, it’s a treasure trove for GMs looking to bring religion and cosmology to life at the table.