Agamemnon line 1

. . . until times within living memory the exponents of Aeschylus were necessarily and properly engrossed by the preliminary difficulties of language and grammar ~ A.W. Verrall

The opening line of the Agamemnon has the watchman begging the gods to free him -- from πόνος:

θεοὺς μὲν αἰτῶ τῶνδ᾽ ἀπαλλαγὴν πόνων  Ag. 1

I ask the gods for release from these ordeals [ponoi] of mine,

He opens this tragedy spying light, fire relayed from the burning city of Troy to Agamemnon's Mycenae. His reads that light, which opens into a question of ultimate cause and import, as a signal. We see him no more - his prayer has been answered, the light has freed him from his πόνος.

The word signifies work, labor, but then broadens to aggregate all kinds of difficulty:

II. stress, trouble, distress, suffering, Il.19.227; “Τρώεσσι πόνον καὶ κήδε᾽ἔθηκεν” 21.525; “ἦ μὴν καὶ π. ἐστὶν . .” 2.291; ἐν τούτῳ τῷ π., of a storm, Hdt.7.190; ὁ Μηδικὸς [π.] the trouble from the Medes, Id.4.1; “παῦροι ἐν πόνῳπιστοί” Pi.N.10.78: freq. in Trag., “πόνος πόνῳ πόνον φέρει” S.Aj.866 (lyr.); “πόνον ἔχειν” Id.OC232 (lyr.), etc.: in pl., sufferings, A.Pr.66, 328, etc.; πόνους πονεῖν (cf. “πονέω” B.1.2); “διά τινα πόνους ἔχειν” Ar.Ec. 975 (lyr.); also of disease, “κατέβαινεν ἐς τὰ στήθη ὁ π.” Th.2.49; “πλευρᾶς πόνοι καὶθώρακος καὶ ἥπατος” Dsc.1.2; ἰσχίων π. καὶ πλευρᾶς ib. 73.

2. pain, esp. physical, “δύο π. ἅμα γενομένων, μὴ κατὰ τὸν αὐτὸν τόπον, ὁ σφοδρότερος ἀμαυροῖ τὸν ἕτερον” Hp.Aph.2.46, etc.

A few lines further along, the watchman repeats his plea for release, using the same words, and makes a wish -- for good news:

νῦν δ᾽ εὐτυχὴς γένοιτ᾽ ἀπαλλαγὴ πόνων 

εὐαγγέλου φανέντος ὀρφναίου πυρός.  (Ag 20-21)

But tonight may there come a happy release from these ordeals [ponoi] of mine!

May the fire with its glad tidings (εὐαγγέλου) flash through the gloom!  (Smyth, Nagy et al)

The light that frees the watchman from his care will determine the courses of the city and its king, and the lives of his successors and heirs. The signal from Troy -- a compound of intelligible light and potent flame, carries a seething contagion through the lives of all who think it is "good news" -- a message of freedom from πόνος, of hope and a turn toward peace.

The opening is the experience of this news -- that is, its portentous power turns on what this light reveals, what lies in shadow -- thus upon reading and misreading, and on what it can and will set ablaze. Behind this telegraph contrived to give earliest notice of the supreme triumph of Agamemnon will lurk love, betrayal, vengeance, hubris, murder of children, political choices, war, spoils, destruction, interpretation of signs, prophecy, bad manners, and the beginnings of a superceding order.

If Aeschylus is anything, he's a firehose of Greek insight, myth, rigor, valor, and poetic power. His text is difficult, corrupt, and long was a mystery to most readers, well after Sophocles and Euripides had been knowledgeably edited, as noted (above) as recently as 1889 by A.W. Verrall. In short, he presents ponos -- difficult interpretive work both for what he did make, and for all the garbled, missing, interpolated things he didn't. He brings news -- it will be a while before we have any idea whether it's the kind of liberating news we're happy to hear.

Leda's children

Leda and the Swan - Francesco Melzi, from a lost work of Leonardo da Vinci

The Greek fascination with symmetrical pairs is latent in this myth of Leda giving birth to two eggs, each holding twins. One egg held the Dioscuri, Castor and Polydeuces. As with the tale of Theseus, the parentage of the Dioscuri was uncertain. It seems Castor was actually the child of Tyndareus, and therefore mortal. Polydeuces was the immortal son of Zeus.

So much for the oversimplified phrase, "point of origin."

The same goes for the other egg, which contained Helen and Clytaemnestra -- Helen, of Zeus, and Clytaemnestra, of Tyndareus. These "twin" sisters married the brothers, Menelaus and Agamemnon, sons of Atreus and Aerope. 

Aerope, daughter of Catreus and therefore granddaughter of Minos, contributed to the horrific division between Atreus and Thyestes. Indeed, traced in detail, the trajectories of Catreus and his descendants had fateful impacts not only on the Pelopids, but later down the line on Menelaos, Agamemnon and Cassandra.

The Killing of Agamemnon

The Killing of Agamemnon

Calyx krater, Dokimasia Painter, 460 BC:

Here Agamemnon, diminished in stature and dripping wet, is trapped in a net, while Aegisthos stands over him, ready to strike with his sword. Behind Aegisthos, Klytaimnestra carries a double ax to lend a hand. A larger image and other views of the krater can be found at this link.

The other side features the vengeance of Orestes upon Aegisthos. Elektra is there. Klytaimnestra enters with her double ax (the labrys).