Melchizedek, a.k.a. the King of Salem, is the first "Warrior of Light" that Santiago meets and the one who changes his destiny forever.
But it doesn't exactly get off to a good start. Just when Santiago is planning to win the heart of the merchant's daughter, an old man—who seems kind of like the annoying people who won't shut up on airplanes, shows up and interrupts him. It turns out to be Melchizedek, who gets Santiago's attention, and not in a good way, when he says that he's already read the book—and that it's irritating. But when he reads Santiago's mind, things get really interesting. Finally it's Santiago who does the asking:
"Where are you from?" the boy asked.
"From many places."
"No one can be from many places," the boy said. [. . .]
"Well, then, we could say that I was born in Salem." (1.88-91)
Now we're getting some cold, hard facts. But before you start brushing up on your witch-trial history, think again. It turns out that, in the Old Testament, Melchizedek was the King of Salem (therefore not the Colonial American city), and was rewarded 1/10 of Abraham's treasure for blessing him.
Record scratch! One-tenth… one-tenth … that sounds familiar. Yep. When Santiago tries to leave after talking to Melchizedek for a while, the old man stops him: "Give me one-tenth of your sheep,' said the old man, 'and I'll tell you how to find the hidden treasure" (1.104).
Okay, Coelho, we got it. This guy is the basically the Bible character himself, appearing to our buddy Santiago sometime long after the time of Abraham. Strike that. He is the Bible character. After Santiago heads to Africa, "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" (1.187). He's not just some small-bit king from a random book of the Bible no one reads; in The Alchemist, he's an immortal being appearing throughout the centuries and doing his "work," helping people achieve their Personal Legends.
One last thing. Besides reading Santiago's mind and writing his life story in the sand, Melchizedek also shows off his kingliness with some fancy-schmancy duds:
The old man opened his cape, and the boy was struck by what he saw. The old man wore a breastplate of heavy gold, covered with precious stones. [. . .]
He really was a king! He must be disguised to avoid encounters with thieves.
"Take these,' said the old man, holding out a white stone and a black stone that had been embedded at the center of the breastplate." (1.166-68)
This breastplate is even cooler than He-Man's—and definitely more Biblical. Later on, the Englishman will tell Santiago that the priests in the Bible carried Urim and Thummim in a golden breastplate, which inserts Melchizedek right back where we found him, smack in the middle of the Old Testament. His clothes, as well as his actions, let us know that Melchizedek isn't just pulling Santiago's (or our) leg; he's the real deal.