Iberia and the Languedoc produced an unusual amount of religious diversity and an unusual amount of documentation about it, and the documentation exists because the diversity was being prosecuted.
Inquisition registers are among the most detailed sources in this atlas for what ordinary people believed. Depositions record household practice, prayers, food rules, what a neighbour was seen doing and when, at a level of granularity no devotional text supplies. Much of what is known about Cathar belief in the Languedoc, and about the practice of Jewish and Muslim converts and their descendants in Spain and Portugal, comes from such registers.
They must be read for what they are. Testimony given to a tribunal with power to imprison, confiscate and execute is shaped by that fact; questioning followed prepared lists, so answers follow the shape of the questions; and denunciation had uses that had nothing to do with religion. A register tells you reliably what was asked and what was said, and only inferentially what was done.
The same centuries produced the region's most consequential positive contribution. The Zohar appeared in Castile in the late thirteenth century and became the central text of the kabbalistic tradition, and the expulsion of 1492 scattered that tradition across the Mediterranean, where it was reworked in Safed and elsewhere.
The archive and the exile are two halves of one history.