where did the office of principal sojourner come from in the royal arch and what are his duties

By 1765, the Royal Arch structure transitioned from a Craft-style officer arrangement to a dedicated chapter system, establishing an officer hierarchy that included three Principals, two Scribes, and three Sojourners led by the Principal Sojourner, as a paper read before Quatuor Coronati Lodge explains.

The Principal Sojourner serves as the primary officer among the three Sojourners who conduct candidates through the Exaltation ceremony and present the dramatic narrative recounting the discovery, as the United Grand Lodge of England states. Within this narrative, the Sojourners describe returning from Babylonian bondage to Jerusalem to assist in rebuilding the temple, where they clear the ruins and uncover an ancient archive 1.

Wilmshurst takes the arrangement of the chapter to be an allegory of the candidate's inner transformation. In his reading, the three Sojourners stationed in the West represent the candidate's psychic and materialized pole, acting as the earthly counterpart to the three Principals who occupy the spiritual pole in the East 1. The journey narrated by the Sojourners symbolizes the candidate's own awakening from the confusion of material existence to rebuild his spiritual self 1.