Liber Fanatica was founded by a group of playtesters in early 2005, before the second edition of WFRP had been officially released. Through the playtest forums, where fans had exchanged many opinions about WFRP, it became evident that the new edition would be unable to accomodate everyone's ideas.

Liber Fanatica was conceived as a resource for both new and old players of WFRP. Its original purpose was to provide an outlet for ideas that had been spawned during the playtest, but which would not see official publication. Following WFRP2's release, Liber Fanatica expanded to include authors who had not been involved in the playtest, but who had articles of their own to contribute. As a collaborative effort, Liber Fanatica ensures fan material is internally consistent and peer reviewed.

Liber Fanatica also serves as a conversion guide for players who wish to update their first edition campaigns to second edition, or who want to use some elements of the new rule set while preserving the play style of the original. As a bonus, the Liber Fanatica writers offer suggestions for expanding the game system in directions that are outside the scope of the new rulebooks; and in some cases beyond what the first edition supplements had covered.