a son of Thyestes, who unwittingly begot him by his own daughter Pelopia. Immediately after his birth he was exposed, by his mother, but was found and saved by shepherds and suckled by a goat, whence his name Aegisthus. Subsequently he was searched after and found by Atreus, the brother of Thyestes, who had him educated as his own child, so that every body believed Aegisthus to be his son.
In the night in which Pelopia had shared the bed of her father, she had taken from him his sword which she afterwards gave to Aegisthus. This sword became the means by which the incestuous intercourse between her and her father was discovered, whereupon she put an end to her own life.
Atreus in his enmity towards his brother sent Aegisthus to kill him; but the sword which Aegisthus carried was the cause of the recognition between Thyestes and his son, and the latter returned and slew his uncle Atreus, while he was offering a sacrifice on the sea-coast.
Aegisthus and his father now took possession of their lawful inheritance from which they had been expelled by Atreus.
Homer appears to know nothing of all these tragic occurrences,
and we learn from him only that, after the death of Thyestes,
Aegisthus ruled as king at Mycenae and took no part in the Trojan
expedition. (Odyssey of Homer
iv) While Agamemnon, the son of Atreus, was absent on his
expedition against Troy, Aegisthus seduced Clytemnestra, the wife
of Agamemnon, and was so wicked as to offer up thanks to the gods
for the success with which his criminal exertions were crowned.
Homer iii) In order not to be surprised by the return of
Agamemnon, he sent out spies, and when Agamemnon came, Aegisthus
invited him to a repast at which he had him treacherously
murdered. After this event Aegisthus reigned seven years longer
over Mycenae, until in the eighth Orestes, the son of Agamemnon,
re turned home and avenged the death of his father by
putting the adulterer to death.