The Story of Iphigenia.

In the Iliad Agamemnon offended the goddess Artemis so he could not go to troy and rescue Helen.
The only way out of being stuck in Greece was to sacrifice his daughter Iphigenia to Artemis.
His wife Clemestria was so mad at him that when he came home from troy she killed him.
After that she killed his second wife who was a princess of troy Cassandra.
Later her other children Orestes and Electra killed her.