After Achilles acquired Briseïs as a slave (after having killed his husband King Mynes of Lurnessus), he tasked Patroclus to take her to their camp and treat her well.
As Achilles had retreated for months from the battlefield after a quarrel with Agamemnon (who had claimed Briseïs as his own), Patroclus donned his armor.
Leading the Argive host, he was feared by the Trojans who believed him to be Achilles, until Hector slew him. Achilles then returned to kill Hector.
Patroclus was mourned by Achilles and Ajax, who were there cut from the battle's tumult where the Amazons and Trojans led by Penthesilea were rampaging the Argives' ranks. They eventually heard it and left Patroclus' grave.
As the Olympians assaulted Japan's hell to retrieve Ares' son from Mikaboshi, Achilles and Patroclus battled. They tried to assist Hercules after he was attacked by a centipede-like beast, but were ineffective. They were finally saved by the timely arrival of the Eastern Gods.