Argos King Acrisius learned from an oracle that he would be killed by the son of his daughter Danae. To prevent this fate, he imprisoned Danae in a bronze tower.
Zeus transformed into a golden rain and met with Danae, and she gave birth to a son named Perseus.
After Perseus was born, Acrisius placed him and his mother Danae in a box and cast them into the sea. Zeus protected the mother and son drifting in the sea, guiding the box through storms until it finally washed ashore on the island of Seriphos, near the coast.
On the island, there were two brothers, Dictys and Polydectes, who ruled over Seriphos. Dictys was fishing by the sea when he saw a wooden box floating in the water. He quickly pulled it ashore. Back at home, the two brothers felt great sympathy for the abandoned and distressed people, so they took them in.
Dictys' older brother Polydectes fell in love with the beautiful Danae, Perseus's mother. He was determined to send Perseus away to prevent him from interfering in his plans with Danae. However, Perseus saw through his intentions. At a banquet hosted by Polydectes, Perseus volunteered to bring him a gift. Polydectes maliciously requested the head of Medusa, the youngest of the three Gorgon sisters known as the "snake-haired Gorgon," who had a reputation for her ability to turn people into stone.
Medusa was once a beautiful goddess but was cursed by Athena and transformed into a being with a snake's body, a head full of snakes, bronze scales on her skin, golden wings on her back, and the power to turn anyone who looked into her eyes into an "ugly" monster statue—though the definition of "ugly" was subjective. Anyone who has seen Medusa's image knows that she was actually quite beautiful, whether in sculptures or the illustrated cards of Fate/Stay Night (interested friends might want to take a look at the sculptures that have been passed down to this day; they are really quite beautiful).
Perseus, young and full of vigor, fearless and determined, accepted the challenge. He prepared himself and embarked on his journey.
The gods blessed this brave young man (Athena wanted to completely get rid of Medusa and secretly planned everything).
Hades lent him a cloak, Athena lent him a shield, and Hephaestus lent him winged sandals and Harpe. With these treasures and his wit and strength, Perseus successfully beheaded Medusa.
Even after her death, Medusa's severed head still retained its petrifying ability. To avoid being petrified, Perseus placed Medusa's head in a bag he carried with him and presented the trophy to Athena.
After Perseus's death, Zeus elevated him to the heavens, becoming a "constellation of heroes." This well-known legend was sublimated into an immensely powerful Noble Phantasm.
Shinji used the "Harpe," forged by Hephaestus, to kill the monsters summoned by Caster.
The part of Medusa's head that petrifies and seals the swarm of insects is called the Pertifying eyes, known as "Cybele."
The bag that holds the majority of Zouken's sealed soul is called the "Bag of Monster Heads."
The means of flying through the night is the Winged Sandals borrowed from Hephaestus.
The ability to change appearance and hide one's form is the cloak borrowed from Hades.
The shield borrowed from Athena is used to fend off tentacle strikes. Like Iskandar's chariot, it is part of a combined Noble Phantasm and the only means of victory that Shinji finds.
Legend has it that after Perseus returned the shield and presented Medusa's head, Athena affixed Medusa's severed head to the center of the shield, transforming it from a purely defensive shield to a versatile offensive and defensive Noble Phantasm, truly making it "Aegis" and shifting its designation from "Zeus's Shield" to "Athena's Shield."
Because the act of embedding Medusa's head was personally done by Athena and not part of Perseus's legend, Perseus's Noble Phantasm still separates the head from the shield.
Petrification is a gradual process that occurs from the outside to the inside. The highest level of petrification is Medusa's Petrifying Eye, which takes about ten seconds to petrify a large volume of tentacles.
Medusa's Eye is the most consuming among the listed Noble Phantasms, requiring Shinji to concentrate his entire body's magical energy. At this time, he cannot use magecraft to enhance his physical abilities. Ten seconds is enough time for the tentacles to partially petrify and crush him.
To achieve victory, Shinji intentionally allows the tentacles to entwine him and manifests the shield regardless of the depletion of magical energy. Under the protection of the shield, Shinji buys enough time and successfully recreates the legend of "Athena's Shield."
Now, the shield that belongs solely to the goddess of wisdom and war, Athena, is complete.
Gorgon, the Monster Queen with snake hair, Medusa, awaken!
The golden radiance emitted by the shield instantly dims the underground waterway, just like the shadow that covers the center of the shield. Everything seen through the golden snake's eyes is covered in green and gray, accompanied by a faint "crack" sound.
Under the Petrifying Eye "Cybele," anything with a magic power rank of C or below is unconditionally petrified.
The foremost tentacle monster begins to turn to stone from its outer layer, and the petrification quickly spreads to its mouthparts and body.
At this moment, the tentacle monster is still unaware of the danger and continues to tighten. The consequences of the friction and compression between the partially petrified and not very hard parts of the tentacles and the divinely crafted shield can only be one thing—complete collapse, turning into stone debris scattered on the ground.
A few seconds later, the tentacles in front of the shield are destroyed. The skill of entwining is most effective when it is continuous, but one uncontrolled section of the entwined tentacles naturally unravels.
The crisis is over, and it's now Shinji's turn to counterattack.
He disregards checking his injuries and immediately retracts "Athena's Shield," launching a series of scythe strikes with his other hand.
Since he has obtained Perseus's Noble Phantasm, he naturally wants to make good use of it. Half of Shinji's learned martial arts are related to scythes.
Through the long years, Scathach has mastered the use of all weapons in the world, including scythes. Under her guidance, Shinji has made significant progress in using the scythe.
He no longer swings it recklessly based solely on his strength and the special effects of the Noble Phantasm, but now knows how to hook, pull, tease, cut, and combine various basic movements into a continuous combo.
This combo starts by using the outer blade of the Harpe to diagonally cut from the upper right to the lower left, followed by a hook and a pull with the inner blade, and finally ends with a horizontal slash.
In the blink of an eye, the tentacle monsters that have been wreaking havoc and destroying a large area of the underground water network are torn apart. The effects of "Refraction of Longevity" deprive the tentacles of their regenerative abilities, and their fate is only one—destruction.