The following source books contain core mechanics that are relevant for the campaign:

Core Rulebook: Pathfinder 1e, as defined by Core Rulebook, is as the base game system. This campaign only uses the mechanics of the Core Rulebook, excluding alignment. This means that races, classes, skills, feats, equipment, spells, magic items, or any other "filling" is only available if listed on the Rules wiki. Note that most of the skill and feats from Core can be ported directly, some spells will need adjustments based on Spell Adjustments, and all classes and magic items will most likely need some rewriting to fit the campaign.

The specific mechanics this campaign cares about are those in Chapter 1, Chapter 3 (character advancement), Chapter 4, Chapter 5 (prerequisites and types of feats), Chapter 6 (usage of weapons and armors, not the specific statistics), Chapter 7 (vital statistics, movement, exploration), Chapter 8, Chapter 9 (casting spells, how to read spell descriptions), Chapter 13 (dungeons, traps, sample traps, wilderness, urban adventures, weather, environmental rules), Appendix 1, Appendix 2.

Occult Adventures: this campaign uses the base mechanics of the Occult Adventures book, excluding any alignment usage. Again, this means that races, classes, skills, etc. are only available if listed on the Rules wiki. The mechanics this campaign cares about are those in Chapter 3 (types of feats), Chapter 4 (psychic magic), Chapter 5 (possession).

Mythic Adventures: This campaign uses the base mechanics of the Mythic Adventures book, excluding any alignment usage. Once again, this means that any actual content such as mythic paths, path abilities, universal mythic abilities, feats, spells, magic items, etc. are only available if listed on the Rules wiki. The mechanics this campaign cares about are those in Introduction, Chapter 1 (creating a mythic character, base mythic abilities), Chapter 2 (types of feats).

Note that mechanics listed with these source books might be removed from this list to be placed on the Rules wiki, especially if said core mechanics have been revised to better match the campaign. This is especially likely for mythic progression, mythic paths, and the base mythic abilities based on the way the campaign unfolds.

Some of the content on the wiki might refer to other source books (such as the bestiary, in case of summoning spells). Such a reference only refers to the minimum required, and always excludes any alignment usage.