Perseus and Andromeda (Leighton) daughters of Poseidon, the god of the sea. When the nymphs became aware of her claims, they protested to their father, who retaliated by calling up a sea monster called Cetus to patrol and wreak havoc along the coastline of Ethiopia placing Cassiope's kingdom at risk. In response the Queen, together with her husband Cepheus, decided to sacrifice her daughter, Princess Andromeda, to the monster. Andromeda was chained to a rock at the edge of the sea as an offering to the monster. Perseus was travelling back home on his winged horse, Pegasus, after battling with Medusa. He rescued Andromeda
Perseus Then, accused by Acrisius of lying about having slain Medusa, Perseus proves himself by showing Acrisius the Gorgon's head, thus fulfilling the prophecy. Having killed Acrisius, Perseus, who was next in line for the throne, gave the kingdom to Megapenthes ("great mourning") son of Proetus and took over Megapenthes' kingdom of Tiryns. The story is related in Pausanias, which gives as motivation for the swap that Perseus was ashamed to become king of Argos by inflicting death. In any case, early Greek literature reiterates that manslaughter, even involuntary, requires the exile of the slaughterer, expiation and ritual purification. The exchange