Upon learning about Patroclus' death, Achilles is overcome with grief, anger, and guilt. Achilles felt responsible for Patroclus' demise since he had withdrawn from the war, making himself and by extension, Patroclus vulnerable to attack. The desire for retribution against Hector and avenging the loss of his beloved friend becomes Achilles' primary motivation for re-entering the conflict. Achilles sets aside his earlier resentment against Agamemnon and reconciles with the Greek forces to participate in the battle once more.
Achilles enters the battlefield consumed by rage and armed with new armor crafted by Vulcan at Aphrodite's request. His thirst for vengeance turns him into an unstoppable force that drives a terror into the hearts of the Trojan army. Achilles ultimately engages in a single combat with Hector and eventually slays him in a dramatic turn of events, fulfilling his vow to honor Patroclus.