The Sphinx was another monstrous daughter of Typhon and Echidna. She had the head and breasts of a woman, the body of a lion, and the wings of a bird of prey. A vicious, man-eating monster, the Sphinx enjoyed playing with her food like a cat toying with a mouse. Her favorite game offered her victims a riddle to solve. If the victim could solve the riddle, the Sphinx promised to let the person go. Although many tried, they all failed and were devoured.

The Sphinx lived in the mountains outside Thebes, where she harassed travelers and residents of the city. Oedipus, traveling to Thebes, encountered the Sphinx, who stopped him and demanded that he try to answer her riddle: “What creature walks on four legs in the morning, two at noon, and three in the evening?”

Unlike those who'd tried and failed to answer this puzzling riddle, Oedipus answered, “Man.” In the “morning” of life (that is, in infancy), a baby crawls on all fours; at “noon,” or the prime of life, a person walks upright on two legs; in the “evening” of life, an old person relies on a cane.

Oedipus gave the correct answer. The Sphinx was so shocked and furious that she threw herself off a cliff. The city of Thebes was saved. In gratitude, the people made Oedipus their king and gave him the hand of Jocasta, the recently widowed queen. (To find out why Oedipus's reward was actually a huge problem for him, read Chapter 19.)