Thyestes is a king of Mycenae in Greek mythology, the son of Pelops and Hippodamia and the brother and rival of Atreus. Contending for the throne of Mycenae, he seduced his brother's wife Aerope and obtained through her the golden lamb on which the kingship depended; Zeus declared for Atreus by reversing the course of the sun. In revenge for the adultery Atreus killed Thyestes' sons and served them to their father at a banquet — the "Thyestean feast" that made the house of Pelops a byword for inherited horror. An oracle told the exiled Thyestes that only a son born of his own daughter Pelopia could avenge him; that son, Aegisthus, killed Atreus and went on to haunt the next generation of the house.
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I.The contest for Mycenae
After the murder of their half-brother Chrysippus, Thyestes and Atreus fled their father's country and were received at Mycenae, whose vacant throne fell to the line of Pelops. The brothers' rivalry turned on a golden lamb: Thyestes, who had seduced Atreus' wife Aerope, obtained the lamb through her and produced it to claim the kingship.
Zeus signalled the true order of things by turning the sun back in its course, and on that portent Atreus took the throne and drove Thyestes into exile.
II.The feast
Feigning reconciliation, Atreus recalled his brother and set before him a banquet cooked from Thyestes' own sons — in Apollodorus' account Aglaus, Callileon and Orchomenus. When the meal was done Atreus showed him the hands and feet, and Thyestes fled cursing the house.
The meal became proverbial: a "Thyestean feast" is still a name for the unspeakable banquet.
III.Pelopia and Aegisthus
An oracle promised vengeance only through a son begotten on Thyestes' own daughter, Pelopia. Aegisthus, the child of that union, was exposed at birth, suckled by a goat, and raised unknowing in Atreus' own house.
Sent by Atreus to kill Thyestes, Aegisthus recognised his father by the sword Pelopia had taken from him, turned the blade on Atreus instead, and set Thyestes on the throne of Mycenae — until Agamemnon and Menelaus returned in force and drove him out for good.
IV.Afterlives
Thyestes' story was a favourite of ancient tragedy: the plays Sophocles and Euripides devoted to him are lost, but Seneca's Thyestes survives as the darkest full telling. Through it the feast passed into the European imagination as the very type of the inherited curse.