The ordinary world Perseus had lived on was the island. Perseus had grown up on this island. Once he was grown he became a strong young man that became a fisherman.
Meeting with a Mentor
The call to adventure was when Perseus went to Polydectes wedding. This was because Perseus didn't bring a gift to the wedding. Therefore since he was sent to get Medusa's head as a gift.
Crossing the Threshold
The refusing call to adventure would be when Perseus was hesitant on where Medusa was. Perseus had to find Medusa as the present for the weeding. He had been hesitant on trying to find Medusa because he had been unsure of where she was.
Test, Allies, and Enemies
Hermes the messenger of the gods, assisted Perseus in finding the three gray women. Who knew how to get to the nymphs of the north. He also would help him get to Medusa and get the head of the creature so he could bring it back to Polydectes.
Perseus, following Hermes to gather materials is the ultimate Crossing the Threshold moment. Where there is no turning back. He first stared by finding his way to the nymphs, then, gathered the items from the nymphs.
Perseus' ally Hermes, was acting as his consort/mentor guiding him throughout the adventure. Medusa, acting as Perseus' enemy, made the journey the most perilous. Lastly, his test was with the three gray women where he had to steal their eye which made it less reluctant so they could see again.