How we cite our quotes:
(Chorus): "[Helen] flitted lightly off through the gates
and was gone, her daring past all daring.
With much groaning the house-prophets spoke:
'The house! Oh, the house, alas, and its chiefs!
The marriage-bed, the steps of a wife in love!
Here is silence, and dishonor seen
in those deserted; and they do not revile, they do not plead.
In his longing for her over the sea
her phantom will seem to rule in the house.'" (407-415)
These words point out a basic precondition for revenge: memory. You can't set out to take vengeance on somebody if you don't remember the bad things they did to you. Here, we see how the memory of Helen makes her absence sting like crazy. This helps explain the incredible revenge Menelaus and Agamemnon got against the Trojans.
(Chorus): "Long spoken among men, there exists an old saying
that a man's prosperity grown
fully great has offspring, not dying
childless; his line's good fortune
bears shoots of insatiable woe.
I differ from others, alone in my thinking:
it is the impious deed
which later on begets
more deeds that resemble their own parentage;
for to houses upright and just
fine children are destined forever." (750-762)
Here, once again, we've got the Chorus making a fairly confusing and metaphorical statement out of something that could have been put a lot more simply. When they say "it is the impious deed / which later on begets / more deeds that resemble their own parentage," couldn't that just be rephrased as, "when you do bad things to other people, they do bad things to you"? Looked at in this way, it's pretty clear that the Chorus is talking about the vicious circle of revenge.
(Cassandra): "Oh! Oh, this misery! Deep down again the fearsome work of truthful prophecy agitates and whirls me round with its stormy prelude. You see these young ones seated by the house, resembling dream-shapes? They are children killed, as if by people outside their family! Their hands are full of their own flesh for meat, clearly visible, holding their entrails and the vitals with them, most pitiable burden, which their father tasted. For that, I say that someone is planning retribution, a cowardly lion who roams free in the marriage-bed and has stayed at home – alas it is against the master on his return." (1214-1227)
Here, Cassandra reveals the horrible crime of Atreus. This crime will inspire Aegisthus, the brother of the slaughtered children, to take revenge against Atreus's son, Agamemnon.