The True Name of the Heroic Spirit of the Class Card is Gilgamesh, humanity's most ancient hero. As he was the king who obtained all the world's treasures and stored away the original of every Noble Phantasm, he can appropriately be called the apex of Heroic Spirits that no proper Heroic Spirit stands a chance against.
Gilgamesh appears as a black shadow of his original form, completely covered in black mud.
Corrupted Archer as seen in the anime adaptation.
Fate/kaleid liner PRISMA☆ILLYA 2wei!
The eighth Class Card that holds Gilgamesh was located at the center of one of Fuyuki's ley lines, where it continuously absorbed mana for two and a half months, shrinking it considerably and becoming stronger than any of the previous Heroic Spirits. Because it was deep underground, it took much excavation just to enter its Mirror World. Illyasviel von Einzbern and her group prepare to face it with all their strength, but despite their best efforts, they are not able to defeat it.
Bazett Fraga came close to gouging out the card from its body, identifying it as Archer before being forced out. As it calls out for the Holy Grail, Archer brings out Ea, causing the girls to flee from the Mirror World due to its overwhelming power. To their surpise, Archer follows them through a crack in space caused by Ea, forcing Luvia to collapse the excavation site to bury it as they escape.
However, Archer uses Vimana to escape the underground and fly towards the Holy Grail's ritual site at Mount Enzou, where it dropped explosives to expose the cavern within. Archer then lands on the ground below and activates a massive magic formula inside. Signs of the incarnated half of Gilgamesh begin to show on his body, and Illya inadvertently separates the two when she attacked him.
After Illya and the younger Gilgamesh talk, he begins to reveal Miyu's existence as a Holy Grail, just before the shadow Gilgamesh grabs Miyu to use as a vessel for the Grail. The two Gilgamesh then merge back into one, becoming an incarnation of darkness not unlike Angra Mainyu. He fights Illya, but eventually loses despite drawing Ea. Miyu is freed, while the younger Gilgamesh and its corrupted version are separated yet again. Due to a dimensional shift, that version of Mount Enzou returns to Miyu's world, leaving Gil to wander around while the Archer card is retrieved by Angelica.
Gilgamesh makes use of the Gate of Babylon, a key-sword connecting to the golden capital of Babylon. It allows for him to retrieve all of his treasures and utilize them as arrows. His greatest treasure is Ea, a "planet creating weapon that in the distant past separated the sky and earth." He also makes use of treasures like Enkidu.
The Archer Class Card cannot be Included. Any Mystic Code normally utilized to Include will be rejected upon the card being Installed.
Installing the Archer Class Card allows for Gilgamesh's power to be obtained. It is possible for the ego of the Class Card to overwhelm the user, so only Angelica has shown the ability to use it constantly. Miyu is overwhelmed in moments of utilizing it. After Gil is manifested, the treasury is split between himself and the card. Gil has only a fraction of the treasures, but he retains ownership of any he takes back from the card user.
Install (Phantasm Summon)
The ability of humanity's most ancient hero Gilgamesh is obtained. Once, the king who obtained every single treasure in the world's warehouse stored every Noble Phantasm's original. Proper Heroic Spirits have no chance against Gilgamesh. It is appropriate to call him the apex of Heroic Spirits however...
Gate of Babylon: King's Treasure : E~A++
Connects to the golden capital Babylon and pulls out all the Noble Phantasms stored in its treasury. True form is a key-sword.
Currently, the treasury is in the middle of a turf war, split into that of the Gil-card using Angelica and Ko-Gil. Nonetheless currently, the Noble Phantasms Ko-Gil takes out are fundementally low rank ones. That number cannot be compared to the total.
Enuma Elish: Star of Creation that Separated Sky and Earth: EX
Not exactly the Noble Phantasm name but refers to the sword of separation Ea’s full release form. It is considered the planet creating weapon that in the distant past separated the sky and earth. Through compression via alternating inversion a windstorm beyond human understanding faults, dislocating space and time pulverizing the target along with the world.
Enkidu: Chain of Heaven: Rank Unknown
Extremely rare Anti-God weapon that increases in toughness with the target’s Divinity. The details are unclear on how Gilgamesh came to naming this after his ex-friend however he trusts this Noble Phantasm more than Ea.
In the manga it became an inexhaustible, freely stretching, flying, surprisingly convenient tool.
Arrow Protection Amulet: D-
An amulet that Ko-Gil wore. The designed is modelled after solar eclipses. The wearer’s evasion rate is greatly increased and D rank and below projectiles are nullified. The more attacks it nullifies the more gold splinters. Before long the amulet is no more.
Also if thrown at the enemy it emits the light and heat of a small sun. The magnitude of this power is proportional the amount of the amulet that is left.
Cloth of Invisibility: E
The prototype of all Noble Phantasms that “hide the figure.” Things covered or enclosed by this cloth cannot be observed through magecraft and optical means. Against those who solely rely on magecraft to search for enemies, it is incredibly effective. However, sound, smell, body temperature and tracks, etc, are oversights so it is situational.
The cloth has a very complex weave. The the weave is estimated to have reached five dimensions. The complete reproduction of this cloth is impossible for humans.