In Greek myth, Sisyphus was the first king of Corinth. He was also a crafty, wicked man who broke just about every law of human decency.
For example, an important value in Greek society was the code of hospitality. Travelers and guests were under the care of Zeus, king of the Greek gods. For that reason, harming a guest was viewed as a very great crime. Sisyphus took pleasure in killing his guests.
Another example of his vile character is the way he disregarded the code of family loyalty. He consulted the oracle at Delphi for advice as to how he might kill his brother Salmoneus without being caught. The oracle told him that if he had children by the daughter of Salmoneus, they would kill their grandfather when they grew up. Sisyphus lost no time in making his niece pregnant. She had two sons by him, but when she learned his intentions, she killed them.
No one in this family was especially admirable. Sisyphus had a son by another marriage, Glaucus, who fed his horses on human flesh.
Sisyphus had his comeuppance after his death. His eternal punishment was to roll a rock up a hill in Hades. Every time he reached the top of the hill, he lost control of the rock, which rolled back down. The endless futility of his punishment gives us the adjective sisyphean: “endless and ineffective, like the labor of Sisyphus.”