Tutte nel cor vi sento,It is a terrible and uncanny piece, anticipating the bloody mood of Ortrud's curse. Yet unlike that villain of Lohengrin, Elettra seems to be addressing internal spirits, and she does nothing overt to pursue her vengeance.
Furie del crudo averno,
Lunge a sì gran tormento
Amor, mercè, pietà.
Chi mi rubò quel core,
Quel che tradito ha il mio,
Provi dal mio furore,
Vendetta e crudeltà.
And still... Immediately after Elettra's aria we hear a truly infernal storm in the orchestra and chorus, a storm in which one hears much of Don Giovanni's later visitors. Neptune has set the plot proper moving by wrecking Idomeneo's ship and forcing him to promise a sacrifice (of, it turns out, his son and Elettra's desire Idamante) for his own survival. In a sense this is just recapping for the audience what has more or less already been announced by Arbace in the previous scene -- Idomeneo's wreck at sea -- but its timing juxtaposes the knot of the drama with its only human antagonist, and Neptune with her underworld Furies.
The god does take a destructive, demanding role for most of the opera, hounding Idomeneo and his people into fulfilling the impossible bargain. (It is this, I suppose, from which Neuenfels derived the anti-religious premise of his stupid if even more stupidly controversial Berlin staging.) And yet, he is also the one to let them off the hook at the end, accepting love and abdication in the place of (further) death. This dual understanding of the divine seems pretty Greek, but leaves one wondering what exactly the story was supposed to be about.
Perhaps it's a tale about our behavior under misfortune. Ilia and Idamante hold close to love, and they are exalted. Idomeneo pushes others away, and himself into isolation -- and he is stripped of office. And Elettra indulges her envy and resentment, and is struck down by them.
Not exactly innovative, but the real story is in the music, in the how they all bear it.