Agamemnon was a child of the King and Queen of Mycenae.
King Atreus & Queen Aerope
Atreus, Agamemnon's father, murdered the children of his twin brother Thyestes and fed them to him after discovering Thyestes' adultery with his wife Aerope. Thyestes fathered Aegisthus with his own daughter, Pelopia, and this son vowed gruesome revenge on Atreus' children. Aegisthus successfully murdered Atreus and restored his father to the throne. Aegisthus took possession of the throne of Mycenae and ruled jointly with Thyestes. During this period Agamemnon and his brother, Menelaus, took refuge with Tyndareus, King of Sparta. There they respectively married Tyndareus' daughters Klytemnestra and Helen. Agamemnon and Klytemnestra had four children: one son, Orestes, and three daughters, Iphigenia, Elektra and Khrysothemis. Menelaus succeeded Tyndareus in Sparta, while Agamemnon, with his brother's assistance, drove out Aegisthus and Thyestes to recover his father's kingdom. He extended his dominion by conquest and became the most powerful prince in Greece.
Agamemnon's family history had been marred by rape, murder, incest and treachery, consequences of the heinous crime perpetrated by his ancestor, Tantalus, and then of a curse placed upon Pelops, son of Tantalus, by Myrtilus, whom he had murdered. Thus misfortune hounded successive generations of the House of Atreus, until atoned by Orestes in a court of justice held jointly by humans and gods.
Agamemnon gathered the reluctant Greek forces to sail for Troy. Preparing to depart from Aulis, which was a port in Boeotia, Agamemnon's army incurred the wrath of the goddess Artemis. There are several reasons throughout myth for such wrath: in Aeschylus' play Agamemnon, Artemis is angry for the young men who will die at Troy, whereas in Sophocles' Electra, Agamemnon has slain an animal sacred to Artemis, and subsequently boasted that he was Artemis' equal in hunting. Misfortunes, including a plague and a lack of wind, prevented the army from sailing. Finally, the prophet Calchas announced that the wrath of the goddess could only be propitiated by the sacrifice of Agamemnon's daughter Iphigenia. Classical dramatisations differ on how willing either father or daughter were to this fate, some include such trickery as claiming she was to be married to Akhilles, but Agamemnon did eventually sacrifice Iphigenia. Her death appeased Artemis, and the Greek army set out for Troy. Several alternatives to the human sacrifice have been presented in Greek mythology. Other sources, such as Iphigenia at Aulis, claim that Agamemnon was prepared to kill his daughter, but that Artemis accepted a deer in her place, and whisked her away to Taurus in Crimea. Hesoid said she became the goddess Hecate.
Agamemnon was the commander-in-chief of the Greeks during the Trojan War. During the fighting, Agamemnon killed Antiphus and 15 other Trojan soldiers. Agamemnon's teamster, Halaesus, later fought with Aeneas of Italy. The Iliad tells the story of the quarrel between Agamemnon and Achilles in the final year of the war. Agamemnon took an attractive slave, Briseis, one of the spoils of war, from Akhilles. Akhilles, the greatest warrior of the age, withdrew from battle in revenge and nearly cost the Greek armies the war.
Although not the equal of Akhilles in bravery, Agamemnon was a representative of kingly authority. As commander-in-chief, he summoned the princes to the council and led the army in battle. He took the field himself, and performed many heroic deeds until he was wounded and forced to withdraw to his tent. His chief fault was his overwhelming haughtiness; an over-exalted opinion of his position that led him to insult Chryses and Achilles, thereby bringing great disaster upon the Greeks.
After the capture of Troy, Cassandra, doomed prophetess and daughter of Priam, fell to Agamemnon's lot in the distribution of the prizes of war.
Return to Greece
After a stormy voyage, Agamemnon and Kassandra either landed in Argolis, or were blown off course and landed in Aegisthus' country. Klytemnestra, Agamemnon's wife, had taken Aegisthus, son of Thyestes, as a lover. When Agamemnon came home he was slain by either Aegisthus (in the oldest versions of the story) or Klytemnestra. According to the accounts given by Pindar and the tragedians, Agamemnon was slain in a bath by his wife alone, a blanket of cloth or a net having first been thrown over him to prevent resistance. Klytemnestra also killed Kassandra. Her jealousy of Kassandra, and her wrath at the sacrifice of Iphigenia and at Agamemnon's having gone to war over Helen of Troy, are said to have been the motives for her crime. Aegisthus and Klytemnestra then ruled Agamemnon's kingdom for a time, Aegisthus claiming his right of revenge for Agamemnon's father Atreus having fed Thyestes his own children (Thyestes then crying out "So perish all the race of Pleisthenes!", thus explaining Aegisthus' action as justified by his father's curse). Agamemnon's son Orestes later avenged his father's murder, with the help or encouragement of his sister Electra, by murdering Aegisthus and Klytemnestra (his own mother), thereby inciting the wrath of the Erinyes, winged goddesses who tracked down egregiously impious wrongdoers with their hounds' noses and drove them to insanity.