You know about the worship of the True God. The topics you may know about include the True Faith, church traditions, holy symbols, mystics, saints, paladins, and theology.
Synergy: 5 or more ranks in Knowledge (the True Faith) gives you a +1 bonus to the DC of your spells and spell-like effects when the target is an arcane creature. Also, 5 or more ranks in a Knowledge skill related to the topic being investigated gives you a +2 bonus to Research checks. This bonus increase by +1 for every additional 10 ranks (that is, +3 at 15 ranks, +4 at 25 ranks, and so on).