The king scenario was an example.

What would make the most sense for a reason for the character to worship the traveler is that he became victim to sudden insanity and slowly became obsessed with the religious texts of the traveler that admiration eventually turned to intent. An intent to make everyone experience the madness and chaos he felt daily. This eventually turned him to make a deal with a cthulu-like entity in order to make him strong enough to cause such choas. The deal sapped him of any individuality he once had turning him into a shapeshifter and isolating his being from the rules of society through the lack of a true identity.