The Psalter, also known as the Psalms of David, is a collection of 150 psalms, with a tradition spanning thousands of years, well before the coming of Christ to earth.

The Jews, as well as later Christians, believed that these psalms had divine power. This is why they used passages from the psalms both for making amulets and in prayers to exorcise evil forces.

However, there have always been references to the existence of certain secret "keys" to the psalms, which it was claimed that some rabbis and later some Christian monks possessed. The notorious "keys" were nothing more than the secret to the use of each psalm.