The name of the King of Salem is Melchizedek and he acts as Santiago's first mentor, teacher, or spiritual guide. He is a person's introduction to learning about what a Personal Legend is and he helps them to make the choice to follow it. He actually shows up in a person's life when she or he is about to give up on their dreams and follow a life of "safety." Melchizedek reveals that he doesn't always show up in person form, either. Not everyone gets to seem him as the King of Salem. He tells the boy that he shows up as a good idea, sometimes, and makes decision making easier on people. Not only that, but most people don't even realize that he's visited them and helped them out.
As Santiago decides to seek his Personal Legend, he looks back on his encounter with Melchizedek fondly. He remembers the advice and gifts he was given and they keep him motivated not to quit throughout the journey to Egypt.
In the Bible, Melchizedek was a high priest who actually collected tithing from Abraham, the father of the covenant in the Old Testament. For Coelho to select this high priest as Santiago's first mentor in the book is an allegorical choice in itself. He is a very old figure who dates far back in history. Coelho references this himself by saying the following:
"Melchizedek watched a small ship that was plowing its way out of the port. He would never again see the boy, just as he had never seen Abraham again after having charged him his one-tenth fee. That was his work"(33).