Polydectes in Wikipedia
In Greek mythology, King Polydectes was the ruler of the island of Seriphos, son of Magnes and an unnamed naiad. Polydectes fell in love with Danae when she and her son Perseus were saved by his brother Dictys (see: Acrisius). Perseus was very protective of his mother and wouldn't allow Polydectes near Danae. Therefore, Polydectes wanted to get rid of him so he could marry her. He thereby hatched a plot.
Polydectes went under the pretence that he was going to marry Hippodamia, a princess from another land and ordered every man in Seriphos to supply him with suitable gifts. Perseus, however, could not afford an extravagant gift and turned up in the king's court empty handed. Polydectes jeered at the young lad and encouraged the rich nobles to do the same. This caused Perseus to speak up and pledge to get the king anything he desired. Polydectes then announced that he wanted nothing more than the head of the Gorgon, Medusa. Perseus agreed and Polydectes told him that he cannot return to the island without it. Therefore Polydectes, unknowlingly sealed Perseus's fate to have a place in the hall of heroes.
When Perseus returned to Seriphos with the Gorgon's head, he found that, in his absence, his mother was threatened and abused by Polydectes, who made her work as a palace slave. Perseus was outraged and strode into the throne room where Polydectes and other nobles were convening. Polydectes was surprised that the hero was still alive and refused to believe Perseus had accomplished the deed he was sent out to do. Perseus professed that he did slay the Gorgon who was Medusa, and as proof, he revealed the severed head. Polydectes and his nobles were then turned to solid stone.