What set Etruscan religion apart in antiquity, and made the Romans depend on it, was its systematic science of interpreting the will of the gods, the Etrusca disciplina. It had three great branches: haruspicy, the reading of the entrails, above all the liver, of sacrificed animals (trained on models like the bronze Piacenza Liver, its surface divided into the gods' regions); fulgural doctrine, the reading of lightning by the quarter of the divided sky it came from; and the interpretation of prodigies.
Underlying all of it was a template of a sixteen-fold heaven, each region belonging to particular gods, mapped onto liver and landscape alike. The Etruscans also reckoned time in saecula, ages of the world of fixed but god-determined length, and believed their civilisation had an allotted span. This was less a religion of narrative myth than a highly developed technology of divination, and Rome kept Etruscan haruspices on call for a thousand years.