This may be wrong because I haven't heard this story in a while, I've forgotten the names so I could be referring to a different version of Perseus's story
Answer:
King Minos tested Perseus's claim to be a demigod by tasking him with the retrieval of Medusa's head. While this seemed like an impossible task, Perseus was granted Athena's shield which had such a shine to it that it was almost a mirror(and another gift from the god, I believe it was Hermes's boots but am not sure). As Perseus arrived at the Temple of Medusa, the gorgon heard him and attempted to sneak up on Perseus. While she was extremely quiet, Perseus spotted her reflection in Athena's shield and cut off Medusa's head. He brought the head back to King Minos to prove himself.
