In the first years of the Trojan War, Troilus was killed by Achilles, who had already driven off the cattle of Aeneas, and sacked the cities of Lyrnessus (where Achilles captured Briseis) and Pedasus, among others (Proclus, Chrestomathy, i). It is at this time that Achilles captured Lycaon ₁ (son of Priam ₁ and Laothoe ₂, daughter of Altes, king of the Lelegians of Pedasus on the river Satnioeis—Hom.Il.21.85), selling him into slavery in Lemnos (the island in the northern Aegean Sea). Lycaon ₁ recalls the episode when Achilles captured him a second time in the tenth year of the war, only twelve days after his return from Lemnos. Lycaon ₁ then asks once more for mercy:

"I beseech thee by thy knees, Achilles, and do thou respect me and have pity; in thine eyes, O thou nurtured of Zeus, am I even as a sacred suppliant, for at thy table first did I eat of the grain of Demeter on the day when thou didst take me captive in the well-ordered orchard, and didst lead me afar from father and from friends, and sell me into sacred Lemnos; and I fetched thee the price of an hundred oxen ... slay me not; since I am not sprung from the same womb as Hector, who slew thy comrade the kindly and valiant." (Hom.Il.21.74).

...but this time Achilles kills him, throwing his body into the river Scamander.

Apollodorus (Epitome 3.32) says that Achilles killed Troilus in the sanctuary of Thymbraean Apollo, before making his way to Mount Ida to attack Aeneas (who, however, had already fled), before capturing Lycaon ₁ for the first time, and before killing Mestor ₂—another son of Priam ₁—(Apd.3.12.5; Hyg.Fab.90).

A picture which Aeneas sees in Carthage, where he came as an exile after the war, depicted the scene of Troilus' death:

"... Troilus, his arms flung away in flight—unhappy boy, and ill-matched in conflict with Achilles—is carried along by his horses and, fallen backward, clings to the empty car, yet clasping the reins; his neck and hair are dragged over the ground, and the dust is scored by his reversed spear." (Virgil, Aeneid 1.471)

But according to Dictys 4.9, Lycaon ₁ and Troilus were captured at the same time in the tenth year of the war, after the deaths of Sarpedon ₁, Hector ₁, and Memnon. The Trojans had been challenged to come out and fight, and so they did—led by Paris and his brothers—but they soon took to flight. Thus were Lycaon ₁ and Troilus captured by the Achaeans, who cut their throats in cold blood by order of Achilles. The Trojans grieved Troilus' death, says Dictys,

"...for they remembered how young he was, who being in the early years of his manhood, was the people's favorite, their darling, not only because of his modesty and honesty, but more especially because of his handsome appearance."

A few days later, Achilles himself was killed, victim of a plot conceived by Paris and Deiphobus ₁ around the matter of Achilles' love for their sister Polyxena ₁ (Dictys 4.11).

A number of vases, however, show Troilus (with his horses) and Polyxena ₁ as they approach a well to fetch water, being observed or ambushed by Achilles.

Frazer (footnote to Apd.Ep.3.32.a) writes: "Tzetzes says ... that he (Troilus) fled from his assailant to the temple of Apollo, and was cut down by Achilles at the altar. There was a prophecy that Troy could not be taken if Troilus should live to the age of twenty (so the First Vatican Mythographer). This may have been the motive of Achilles for slaying the lad."

Troilus' death in the temple of Apollo is evoked by Statius, Silvae 2.4.33:

"... or Troilus, when the lance from the Haemonian hero's arm (Achilles) caught him as he fled round cruel Phoebus' walls."

The love of Achilles for Troilus is deduced from the cryptic Lycophron (Alexandra 307) and his scholiast:

"Ay! me, for thy fair-fostered flower (Troilus), too, I groan, O lion whelp, sweet darling of thy kindred, who didst smite with fiery charm of shafts the fierce dragon (Achilles) and seize for a little loveless while in unescapable noose him that was smitten, thyself unwounded by thy victim: thou shall forfeit thy head and stain thy father's (Apollo) altar-tomb with thy blood."

Achilles raped Troilus and then beheaded him at the temple of Apollo. Or he lured him with a gift (doves) and then killed him (Serv.Aen.1.474, through Roscher, Lex. 5.1217).

According to Dares (7), Troilus ("though youngest of Priam's sons") supported Paris' idea of sending a fleet to Hellas to obtain reparations for the abduction of Hesione ₂, against the warnings of Helenus ₁. He describes him thus:

"Troilus, a large and handsome boy, was strong for his age, brave, and eager for glory." (Dares 12)

And he also counts him as a general, as when he says: "Agamemnon, Achilles, Diomedes, and Menelaus led forth the army. The forces of Hector, Troilus and Aeneas moved opposite" (Dares 20), or "After three years, the war was resumed. Hector and Troilus led forth the army" (23), or "Priam, therefore, divided the command of his forces between Alexander (Paris), Helenus, Troilus, and Aeneas" at a time when Andromache sent word to Priam ₁ to keep Hector ₁ out of the battle (24).

Later (29), we learn that Troilus' forces confronted Agamemnon's in a battle that lasted seven days, in which "Troilus slaughtered many Greek leaders." After a two-months truce, "Troilus, having wounded Menelaus, pressed on, killing many of the enemy and harrying others" in a fierce battle that only night brought to an end. Then new day and new battle, in which Troilus wounded both Diomedes ₂ and Agamemnon. The Achaeans then ask for a six-months truce, and against Troilus opinion, the Trojan council granted the petition (31).

When the truce was over, Agamemnon (this time supported by Achilles' Myrmidons) confronted Troilus, who, however, put to flight the Myrmidons. He then pressed his attack into the Achaean camp, killing and wounding many, until he was stopped by Ajax ₁. The next day Troilus puts to flight Agamemnon and the Myrmidons once more, after which a thirty-day truce for holding funerals was agreed (32).

When war started again, Troilus defeated Agamemnon and the Myrmidons once more. This time, Achilles (who had kept himself away from battle), seeing the Trojan advance, reentered the battle, but was wounded by Troilus. Achilles stayed out of action for six days because of his wound. Towards the end of the seventh day, Troilus advanced on horseback, causing the enemy to flee. But then Achilles and the Myrmidons came to their rescue, wounding Troilus' horse, and as Troilus was thrown off and entangled, Achilles killed him (33). Achilles then tried to drag off the body, but was wounded by Memnon and forced to yield. The death of Achilles was planned by Hecabe ₁ to avenge the deaths of Hector ₁ and Troilus: Achilles was summoned to come to the temple of Thymbraean Apollo "to settle an agreement according to which she would give him Polyxena to marry". An ambush was set up, and Paris killed Achilles (34).