Which sister supported Orestes in his quest to kill Clytemnestra?

The sister who supported Orestes in his quest to kill Clytemnestra is Electra. In the mythological narratives surrounding the story of Orestes, Electra plays a crucial role as she is deeply affected by the murder of their father, Agamemnon, by Clytemnestra and her lover, Aegisthus. Driven by revenge and a desire for justice, Electra encourages Orestes to take action against their mother. Their bond over the shared trauma of their father's death and their mutual quest for retribution forms a central theme in the myth.

Electra's support for Orestes is not only a matter of loyalty but also reflects her own suffering and desire for justice, making her a vital character in this tragedy. This dynamic is vividly depicted in various literary works, particularly in Sophocles' and Euripides' adaptations of the myth, where Electra's character is often portrayed as determined and resolute in her support of her brother's revenge.