In the Iliad, Apollo disguises himself as the Trojan warrior Agenor to trick Achilles. The deception occurs in Book 21, when Achilles is routing the Trojans near the Scamander River.
Agenor bravely turns to face Achilles, but Apollo rescues him by covering him in mist and carrying him away from danger. The god then assumes Agenor’s appearance and leads Achilles on a chase away from the fleeing Trojan army. Achilles believes he is pursuing the same mortal opponent.
Apollo’s purpose is not to defeat Achilles in a direct fight. Instead, the disguise delays him long enough for the other Trojans to reach safety inside Troy. When Apollo finally reveals himself, Achilles realizes that the pursuit has been a divine diversion.
This episode is easy to mix up with Book 22, where Athena later disguises herself as Hector’s brother Deiphobus. Athena’s trick makes Hector believe he has an ally and prompts him to stop fleeing and fight Achilles. Apollo’s Agenor disguise comes first and protects the retreating Trojans.