This is the (Organization) Lore of a particular cult. It provides knowledge of the legends, history, structure, operation and goals of the Mystery Cult in question.
It includes knowledge of the magics, rites and secret passwords and symbolism of the cult, how to covertly signal membership, and how to assess another magus's membership or non-membership in your cult. Two magi with a score in this ability for the same Mystery Cult may well be able to hold a seemingly innocuous conversation without outsiders understanding the true significance or meaning of their words. Many Mystery Cult specialty books also require a score in this ability to decode their heavy symbolism; this method is used to prevent un-Initiated outsiders learning secrets of the Mystery.
Mystery Cult Lore also covers the ceremonies of the cult, frequently enacted whenever the cult gathers formally. It is also a key knowledge for a Mystagogue's performance of the Initiation Rites, to guide the Initiate through the path of Ordeals, ceremony and meditation, to gain new Virtues.
Cult Lore is passed from Mystagogue to Initiate, from Mystae to Mystae in a chain of living secrets. Some cults also write down their secret lores, as this codifies the Mystery and lets others share the same view of the cult — others prefer the secrecy of the Oral Tradition. Small cults may fade away from lack of members, especially if they are persecuted at some point — but if they committed some of their Lore to writing, the cult may be re-born by those who discover and understand the texts. Some cults risk the loss of secrecy for this very reason — that their secrets and magical rites may not be lost forever. Some magi search for lost texts, containing secret lores of the Ancients, hoping to re-enact the rites and rituals that led the Ancients to power.
In game terms, Experience points in Cult Lore are acquired like any other knowledge — including Teaching, Books, Practice and Exposure. Learning Cult Lore from another ensures that master and pupil share the same rites; learning by yourself generally implies that you have devised your own variant (even \"deviant\") rites and rituals — from such disagreements schisms arise and cults may break up and fragment.
A magus may build the knowledge from 0, even without instruction — but this means they have devised their own cult, and should treat their Lore as a new Lore. (General)