Fate (κήρ, kēr, 'fated death') propels most of the events of the Iliad. Once set, gods and men abide it, neither truly able nor willing to contest it. How fate is set is unknown, but it is told by the Fates and by Zeus through sending omens to seers such as Calchas. Men and their gods continually speak of heroic acceptance and cowardly avoidance of one's slated fate. Fate does not determine every action, incident, and occurrence, but it does determine the outcome of life—before killing him, Hector calls Patroclus a fool for cowardly avoidance of his fate, by attempting his defeat; Patroclus retorts: 
No, deadly destiny, with the son of Leto, has killed me, and of men it was Euphorbos; you are only my third slayer. And put away in your heart this other thing that I tell you. You yourself are not one who shall live long, but now already death and powerful destiny are standing beside you, to go down under the hands of Aiakos' great son, Achilleus.
Here, Patroclus alludes to fated death by Hector's hand, and Hector's fated death by Achilles's hand. Each accepts the outcome of his life, yet, no-one knows if the gods can alter fate. The first instance of this doubt occurs in Book XVI. Seeing Patroclus about to kill Sarpedon, his mortal son, Zeus says:
Ah me, that it is destined that the dearest of men, Sarpedon, must go down under the hands of Menoitios' son Patroclus.
About his dilemma, Hera asks Zeus:
Majesty, son of Kronos, what sort of thing have you spoken? Do you wish to bring back a man who is mortal, one long since doomed by his destiny, from ill-sounding death and release him? Do it, then; but not all the rest of us gods shall approve you.
In deciding between losing a son or abiding fate, Zeus, King of the Gods, allows it. This motif recurs when he considers sparing Hector, whom he loves and respects. This time, it is Athene who challenges him:
Father of the shining bolt, dark misted, what is this you said? Do you wish to bring back a man who is mortal, one long since doomed by his destiny, from ill-sounding death and release him? Do it, then; but not all the rest of us gods shall approve you.
Again, Zeus appears capable of altering fate, but does not, deciding instead to abide set outcomes; similarly, fate spares Aeneas, after Apollo convinces the over-matched Trojan to fight Achilles. Poseidon cautiously speaks:
But come, let us ourselves get him away from death, for fear the son of Kronos may be angered if now Achilleus kills this man. It is destined that he shall be the survivor, that the generation of Dardanos shall not die…
Divinely aided, Aeneas escapes the wrath of Achilles and survives the Trojan War. Whether or not the gods can alter fate, they do abide it, despite its countering their human allegiances; thus, the mysterious origin of fate is a power beyond the gods. Fate implies the primeval, tripartite division of the world that Zeus, Poseidon, and Hades effected in deposing their father, Cronus, for its dominion. Zeus took the Air and the Sky, Poseidon the Waters, and Hades the Underworld, the land of the dead—yet they share dominion of the Earth. Despite the earthly powers of the Olympic gods, only the Three Fates set the destiny of Man.
Kleos (κλέος, "glory, fame") is the concept of glory earned in heroic battle. Yet, Achilles must choose only one of the two rewards, either nostos or kleos. In Book IX (IX.410–16), he poignantly tells Agamemnon's envoys—Odysseus, Phoenix, Ajax—begging his reinstatement to battle about having to choose between two fates (διχθαδίας κήρας, 9.411).
The passage reads:
μήτηρ γάρ τέ μέ φησι θεὰ Θέτις ἀργυρόπεζα (410) διχθαδίας κῆρας φερέμεν θανάτοιο τέλος δέ. εἰ μέν κ’ αὖθι μένων Τρώων πόλιν ἀμφιμάχωμαι, ὤλετο μέν μοι νόστος, ἀτὰρ κλέος ἄφθιτον ἔσται εἰ δέ κεν οἴκαδ’ ἵκωμι φίλην ἐς πατρίδα γαῖαν, ὤλετό μοι κλέος ἐσθλόν, ἐπὶ δηρὸν δέ μοι αἰὼν (415) ἔσσεται, οὐδέ κέ μ’ ὦκα τέλος θανάτοιο κιχείη.
For my mother Thetis the goddess of silver feet tells me I carry two sorts of destiny toward the day of my death. Either, if I stay here and fight beside the city of the Trojans, my return home is gone, but my glory shall be everlasting; but if I return home to the beloved land of my fathers, the excellence of my glory is gone, but there will be a long life left for me, and my end in death will not come to me quickly.
|—Translated by Richmond Lattimore|
In forgoing his nostos, he will earn the greater reward of kleos aphthiton (κλέος ἄφθιτον, "fame imperishable"). In the poem, aphthiton (ἄφθιτον, "imperishable") occurs five other times, each occurrence denotes an object: Agamemnon's sceptre, the wheel of Hebe's chariot, the house of Poseidon, the throne of Zeus, the house of Hephaestus. Translator Lattimore renders kleos aphthiton as forever immortal and as forever imperishable—connoting Achilles's mortality by underscoring his greater reward in returning to battle Troy.
Kleos is often given visible representation by the prizes won in battle. When Agamemnon takes Briseis from Achilles, he takes away a portion of the kleos he had earned.
Achilles' shield, crafted by Hephaestus and given to him by his mother Thetis, bears an image of stars in the centre. The stars conjure profound images of the place of a single man, no matter how heroic, in the perspective of the entire cosmos.
Nostos (νόστος, "homecoming") occurs seven times in the poem, making it a minor theme in the Iliad itself. Yet the concept of homecoming is much explored in other Ancient Greek literature, especially in the post-war homeward fortunes experienced by the Atreidae (Agamemnon and Menelaus), and Odysseus (see the Odyssey).
Pride drives the plot of the Iliad. The Greeks gather on the plain of Troy to wrest Helen from the Trojans. Though the majority of the Trojans would gladly return Helen to the Greeks, they defer to the pride of their prince, Alexandros, also known as Paris. Within this frame, Homer's work begins. At the start of the Iliad, Agamemnon's pride sets forth a chain of events that leads him to take from Achilles, Briseis, the girl that he had originally given Achilles in return for his martial prowess. Due to this slight, Achilles refuses to fight and asks his mother, Thetis, to make sure that Zeus causes the Greeks to suffer on the battlefield until Agamemnon comes to realize the harm he has done to Achilles. Achilles’ pride allows him to beg Thetis for the deaths of his Greek friends and countrymen. When in Book 9 his friends urge him to return, offering him loot and his girl, Briseis, he refuses, stuck in his vengeful pride. Achilles remains stuck until the very end, when his anger at himself for Patroclus’ death overcomes his pride at Agamemnon's slight and he returns to kill Hector. He overcomes his pride again when he keeps his anger in check and returns Hector to Priam at epic's close. From epic start to epic finish, pride drives the plot.[ii]
Akin to kleos is timê (τιμή, "respect, honor"), the concept denoting the respectability an honorable man accrues with accomplishment (cultural, political, martial), per his station in life. In Book I, the Greek troubles begin with King Agamemnon's dishonorable, unkingly behavior—first, by threatening the priest Chryses (1.11), then, by aggravating them in disrespecting Achilles, by confiscating Briseis from him (1.171). The warrior's consequent rancor against the dishonorable king ruins the Greek military cause.
Hybris (Ὕβρις) plays a part similar to timê. The epic takes as its thesis the anger of Achilles and the destruction it brings. Anger disturbs the distance between human beings and the gods. Uncontrolled anger destroys orderly social relationships and upsets the balance of correct actions necessary to keep the gods away from human beings. (footnote Thompson). Despite the epic's focus on Achilles’ rage, hybris plays a prominent role also, serving as both kindling and fuel for many destructive events. Agamemnon refuses to ransom Chriseis up out of hybris and harms Achilles’ pride when he demands Briseis. Hubris forces Paris to fight against Menelaus. Agamemnon spurs the Greeks to fight, by calling into question Odysseus, Diomedes, and Nestor's pride, asking why they were cowering and waiting for help when they should be the ones leading the charge. While the events of the Iliad focus on the Achilles’ rage and the destruction it brings on, hybris fuels and stokes them both.
The poem's initial word, μῆνιν (mēnin; acc. μῆνις, mēnis, "wrath," "rage," "fury"), establishes the Iliad's principal theme: The "Wrath of Achilles". His personal rage and wounded soldier's pride propel the story: the Greeks' faltering in battle, the slayings of Patroclus and Hector, and the fall of Troy. In Book I, the Wrath of Achilles first emerges in the Achilles-convoked meeting, between the Greek kings and the seer Calchas. King Agamemnon dishonours Chryses, the Trojan priest of Apollo, by refusing with a threat the restitution of his daughter, Chryseis—despite the proffered ransom of "gifts beyond count." The insulted priest prays his god's help, and a nine-day rain of divine plague arrows falls upon the Greeks. Moreover, in that meeting, Achilles accuses Agamemnon of being "greediest for gain of all men." To that, Agamemnon replies:
But here is my threat to you. Even as Phoibos Apollo is taking away my Chryseis. I shall convey her back in my own ship, with my own followers; but I shall take the fair-cheeked Briseis, your prize, I myself going to your shelter, that you may learn well how much greater I am than you, and another man may shrink back from likening himself to me and contending against me.
After that, only Athena stays Achilles's wrath. He vows to never again obey orders from Agamemnon. Furious, Achilles cries to his mother, Thetis, who persuades Zeus's divine intervention—favouring the Trojans—until Achilles's rights are restored. Meanwhile, Hector leads the Trojans to almost pushing the Greeks back to the sea (Book XII). Later, Agamemnon contemplates defeat and retreat to Greece (Book XIV). Again, the Wrath of Achilles turns the war's tide in seeking vengeance when Hector kills Patroclus. Aggrieved, Achilles tears his hair and dirties his face. Thetis comforts her mourning son, who tells her:
So it was here that the lord of men Agamemnon angered me. Still, we will let all this be a thing of the past, and for all our sorrow beat down by force the anger deeply within us. Now I shall go, to overtake that killer of a dear life, Hektor; then I will accept my own death, at whatever time Zeus wishes to bring it about, and the other immortals.
Accepting the prospect of death as fair price for avenging Patroclus, he returns to battle, dooming Hector and Troy, thrice chasing him 'round the Trojan walls, before slaying him, then dragging the corpse behind his chariot, back to camp.