Agamemnon: Character Profiles

Aegisthus:  Aegisthus , the son of Thyestes, is bent on avenging on the son of Atreus the wrong done Thyestes by Atreus. His readiness to set himself up as a tyrant and his brutality toward the Chorus make him contemptible, even if he is not as complete a coward as the Chorus say he is. At the least, we can say that he has none of Clytemnestras force of character.
Agamemnon:  In Homers epics, Agamemnon was the king of Mycenae; Aeschylus depicts him as the king of Argos. In other ways, Aeschylus stays close to Homer, presenting Agamemnon as the most powerful of the Greek kings who sailed to Troy and therefore the leader of the Greek army, even though it was his brother, Menelaus, whose wife, Helen, eloped with Paris, a son of the king of Troy. Agamemnon speaks of moderation and of not offending the gods, but in consenting to walk on the purple tapestries his wife strews for him, he reveals the arrogance also shown in speaking of the gods as merely helping him, and in ordering his wife to take care of his concubine.
Cassandra:  Cassandra is the daughter of Priam, king of Troy. She is presented completely sympathetically. Her one mistake was to accept the gift of prophecy from Apollo, and then to refuse to fulfill her promise to sleep with him. Thus, by Apollos curse, her prophecies are always true, but never believed, and she was unable to save her city from its doom. In the Agamemnon, her utter helplessness to prevent the fate she sees coming to Agamemnon and to herself makes her pitiable, while her courage in going to meet that fate makes her admirable.
Chorus and Chorus Leader:  By tradition, one man, the Chorus Leader, speaks for the Chorus during scenes that involve dialogue, but he is not otherwise distinguished from the Chorus as a whole. The Chorus consists of elders of Argos, old men of high birth who were too old to go to Troy. They form the council that assists Clytemnestra to rule while Agamemnon is away. They are loyal to Agamemnon, and they welcome him and later mourn him sincerely, but they are also ready to criticize him when he shows what they consider hubris. They sometimes seem to embody the voice of traditional wisdom, though they are also ready to think for themselves. On the subject of women, they are blinded by their assumptions.
Clytemnestra:  Clytemnestra is Helens sister, or half-sister, depending on which version of the story one follows. She is the daughter of a king, and clearly a powerful and confident woman, embittered by long years of brooding on Agamemnons sacrifice of their daughter, Iphigeneia. So far is she from the Greek notion of what women are like that she is in several places spoken of as thinking like a man, and she resents anyone who dismisses her as womanish.
Herald:  The Herald is Agamemnons official messenger. In his account of the sufferings of the ordinary soldiers, he speaks as one of them. In his pride in the completeness of the destruction of Troy, he embodies the blindness of all to the dangers of such excess.
Watchman:  The Watchman is a simple man, who longs only to be released from his duties and allowed to sleep in a bed. His joy at the news that Troy has fallen and his longing to welcome his master home suggest that the people as a whole are loyal to Agamemnon.