Answer:
I believe that Athena granted him divine vision.
Step-by-step explanation:
"Diomedes received the most direct divine help and protection. He was the favorite warrior of Athena (who even drove his chariot once). He was also the only hero except Heracles, son of Zeus, that attacked—and even wounded—Olympian gods (most notably Ares, whom he struck with his spear). Once, he was even granted divine vision in order to identify immortals."
Hope this helps :D Have a great day :3
N yes... i found this on a website but i wasn't sure what the answer would be... so i just put that specific paragraph down..