“Alas, that it should be the lot of Sarpedon whom I love so dearly to perish by the hand of Patroclus. I am in two minds whether to catch him up out of the fight and set him down safe and sound in the fertile land of Lycia, or to let him now fall by the hand of the son of Meneoetius.”
~ The Iliad - Book XVI (Samuel Butler Translation. p117 / v431)
Patroclus begs Achilles to give him his armor. While Patroclus is wearing Achilles’ armor, the first ship goes up in flame. Achilles calls the Myrmidons and asks them to join the battle under Patroclus’ leadership. He prays to Zeus. Patroclus brings vigor to the battle, the Trojans retreat and Hector flees. Against Achilles’ advice, Patroclus chases the Trojans all the way to the city walls and kills many. Patroclus and Hector fight over the body of Cebriones, the charioteer. Apollo knocks off Patroclus’ helmet, making him dazed, Euphorbus strikes him from behind, Hector kills him.
In Book 16 of The Iliad, Zeus watches his son Sarpedon being attacked by Patroclus and about to be killed. He has the power to save Sarpedon and is conflicted. He wants to save, but his wife Juno (Hera) advises him against it, reminding him of his duty. He might end up setting the wrong example, and other gods also will start favoring their children.