Clytemnestra

Clytemnestra (sometimes incorrectly spelled as Clymenestra) was the daughter of Leda and King Tyndareus of Sparta, and the sister (or half sister) of Helen, and the twins Castor and Pollux (Polydeuces). She married Agamemnon, king of Mycenae (or Argos), and was the mother of Iphigenia, Orestes, Chrysothemis and Electra. While Agamemnon was away at the Trojan War, Clytemnestra began an affair with Aegisthus and plotted with him to kill Agamemnon when he returned form the war (partly in revenge for Agamemnon's sacrifice of their daughter Iphigenia at the start of the war). After Agamemnon's death, she continued to rule as Aegisthus' queen until she was eventually killed by her own son Orestes in revenge for Agamemnon's murder.