Klytaimestra: Agamemnon by Aeschylus
While her husband Agamemnon has been away for ten years fighting the Trojan War, his queen Klytaimestra has been holding down the fort as well as engaging in a liaison with Aigisthos. In addition to being her lover, he is also her co-conspirator in plans for avenging the death of her daughter. The high point of the drama is when she catches the returned Agamemnon unprotected in his bath and proceeds to butcher him like a prize hog.
Orestes and Elektra: Electra by Sophocles
The same family tragedy, but different episode by a different playwright. Orestes and Elektra are brother and sister who have sworn to take revenge upon their mother Klytaimestra and her lover Aigisthos for murdering their father, Agamemnon.
Apollo: Orestes by Euripides
The final chapter in the trilogy stemming from Agamemnon’s death at the hands of his wife has Orestes overwhelmed by guilt at the killing of his own mother. As the play nears its end, both brother and sister are facing an order of execution and conspire to out in a blaze of vengeful glory by killing Helen of Troy and her daughter Hermione. Right at the moment that all the various events are about to collide in an explosion of bloody violence, however, Apollo, god of light and law arrives with plans to press the reset button and put everything back to how it was and fix all the problems that brought upon such disorder. This is the real deus ex machina that you may have heard about elsewhere.
Iphigenia: Iphigenia Among the Taureans by Euripides
Remember there at the beginning in the Aeschylus play the reason that Agamemnon’s wife murders him (apart from the fact that she wants to continue having her fun with Aigisthos, that is)? The daughter whose death Agamemnon was responsible for is Iphigenia. This translation is of a play by Euripides who was not the writer of the version of Agamemnon mentioned above. In this version, the whole resulting lineage of wife killing husband and son killing daughter could have been avoided as just a merry mix-up since it turns out that Iphigenia didn’t actually die in the first place, but was saved at the last second when the goddess Artemis replaced her on the sacrificial altar with a deer.
