King Solomon was revered as the wisest king to ever have ruled. According to the testament of Solomon, an angel visited him and bestowed unto him magical knowledge and a magical ring. this angel gave him the power to control demons. He even admitted to having bound demons to his will and made them build his temple. He put all of his spells and magics in a tome. The Key of Solomon and he is also credited with writing the lesser Key of Solomon, and the Goetta.
After arriving at Bobby's place, Sam finds the Key of Solomon, and is in awe of protective circles inscribed in the book. The Key of Solomon was a powerful spell book written by King Solomon and containing special sigils that can be used against demons. A handwritten copy was owned by Bobby Singer.
Rowena briefly references the Judgement of Solomon from the Hebrew Bible when she says "split the baby."
While Sam uses cinders to draw a devil's trap, Max Banes tells him that he prefers a "Fifth Pentacle of Mars" because it has more character. The Fifth Pentacle of Mars is one of the pentacles inscribed in the Greater Key of Solomon which is used for protection against demons.
While trying to find a way to track down Jack, Sam and Dean receive, from the demon Barthamus, part of a Canaanite tracking spell that dated back to the time of King Solomon. The spell was commissioned by King Solomon to keep tabs on the Queen of Sheba, who was a Nephilim herself.
Learning that they need the Seal of Solomon in order to open a rift to Apocalypse World, Sam begins researching the Men of Letters archives for anything on King Solomon. Among the archives, Dean learns that the Men of Letters found Solomon's treasure in 1917, in what is modern day Israel; among the items in the treasure included a "crystal that glows with an unearthly light." The Seal was sent to Capitulum 7 in Portsmouth, Rhode Island.