The Archer of the previous Grail War. Mankind’s oldest king of heroes, who defeated Saber. For more details, refer to his status screen in the game.
As no proper Heroic Spirit can match this man, he could be called the “Servant Killer.”
Without a doubt, he is the strongest existence amongst the Servants.
Though he lost due to obsession against Saber…
Though he lost due to pride against Shirou…
Though he lost due to carelessness against XXXXX…
…The fact of the matter is that if he actually gets serious, he is a Servant that cannot be rivaled.
Perhaps because he has been living in human society for the past ten years, he seems to be hip on the latest fashions. He owns various casual clothes, but his favorite is the biker outfit he wore in the Rin route.
Well, he liked it enough to overlook Shirou’s group and leave instead of letting it get dirty, at any rate. I can’t believe the protagonist’s life was worth less to Gil than his coat…!
It might seem strange how Gil could live in human society for ten years with a personality like his and not cause a fuss, but Gil must have realized it would have been a problem, too, because apparently he drank a certain Noble Phantasm to change his appearance and personality.
Also, during the design stage, I selfishly insisted that “Gil absolutely has to wear full golden plate armor.”
Why, you ask? Well, it might be because I was repeatedly challenging a certain 60 story tower at the time…

Fate/side material: Fate Encyclopedia

The Archer class Servant of the Fourth Holy Grail War. Though he was summoned by Tohsaka Tokiomi, he ended up deserting his master and re-contracting with Kotomine Kirei. He is the strongest character in both Fate/stay night and Fate/Zero.
In the boy-meets-girl story of the original Fate/stay night he was forced to yield to the universal law of “love conquers all,” but in Fate/Zero he’s free to show off his overwhelming, cheat-like strength without restraint. He could have ended the war in a single night if he truly desired to do so. But then, careless pride is the king’s prerogative, and getting serious over something as frivolous as a wish-granter would be unbecoming. So, taking that into account, it sort of balances out the huge disparity in firepower… I guess?
Also, the reason that he was able to splendidly escape after being swallowed by Angra Mainyu at the end of Fate/Zero despite succumbing to the same thing in the Sakura route of Fate/stay night is because in the latter he was distracted by the presence of a naked girl.
…Just kidding! Actually, it was due to the difference in power between the “mud,” which was cut off from its source, and the “shadow” which was connected directly to it.

Fate/Zero material: Fate/Zero Encylopedia

Gilgamesh is one of the main Servants newly made available in CCC.
He is a half-god, half-human who is the most ancient hero in human history. His origins go back to before the common era. He ruled the Sumerian city of Uruk.
Gilgamesh is ruthless and unfeeling. He is a tyrant who considers his own standards and rules to be absolute above all, so he has no ear for the opinion of humans.
Like Red Archer, this guy has also been explained to death in various Type-Moon works, so there isn’t much in specific to talk about here.
His standard powers, abilities, and character setting have been tuned a bit to fit into the EXTRA world, but he is more or less the same Gil as always.
He is an exceptional Heroic Spirit who proudly flaunts his ornate golden armor. He uses his overly abundant treasures and wealth as if he is trying to get rid of them.
He refers to himself with オレ [ore] but writes it as 我 [which is usually pronounced ware, but Gil pronounces it ore].
His alignment is chaotic good.
He is a cold-blooded tyrant who has had a fun life pursuing all the world’s treasures and pleasures to the limit.
He is a temperamental person, but he doesn’t (usually) doll out the pain simply because he is in a bad mood.
When he does end someone’s life, it’s because they have a disgusting evil soul, or because they are trying to oppose him.

He is a King who lays down judgment equally to all, regardless if they are good or evil.
His absolute standards all revolved around “himself” so he has no sympathy or consideration for the ideas of others.
As far as Gilgamesh is concerned, life is only ever “something that will die right now” or “something that will eventually die.”
If Gilgamesh decides that you are “a life that should die now” it doesn’t matter if you are a wise old man, you’ll be slaughtered.
“What the heck!? So basically you’re just saying that he pays no heed to his rules or conditions, and it all depends on how Gilgamesh is feeling that day!” It’s unavoidable that you want to point this out, but that’s just how being a King is.
Whether his judgment aligns perfectly with the truth of the universe, or he abuses his power in a drunken stupor, whatever he does, his actions as King are indisputable.
This is what it means to be an absolute ruler.
Some may see Gilgamesh’s very egocentric nature as similar to Iskandar’s, but there is one respect in which the two differ greatly. Gilgamesh has no need for vassals.
Gilgamesh is a king who reigns alone from start to finish. He loves “treasure” and “tools.” While “people” are simply things that will eventually disappear.
…No matter how worthy of love a person may be. No matter if he recognizes they are worthy of love.

Also, when it comes to CCC’s main theme, girl problems can’t be avoided [he can’t easily find a girl he likes].
Gil’s type of woman is a “noble maiden” (And when he appears as Young Gil he prefers “wildflower” type girls).
He hates women who, despite continually depending on men, try to manipulate and use men. In other words he dislikes “girlish” women.

Moon Cell reincarnated Gilgamesh after reconstructing him, but Gilgamesh was still unable to be controlled, so Moon Cell sealed him away by sending him to the far side of the Moon.
Gilgamesh didn’t see there being any meaning in the Holy Grail War, so somewhere in the darkness of the far side of the Moon (the sea of corrupted information) he made himself a room to sleep and dozed away to his degenerate dreams.
Unlike the other Servants, Gilgamesh has no intention of making a contract with a Master. Ally of no one. Needed by no one. Perfectly happy idling his time away. However, the fool (the protagonist) who fell down into the hell that is the far side of the Moon spouted some rubbish that were quite amusing to Gil, so he woke from his slumber to interfere a bit. That’s what started their story.
Since Gil had been dozing off in hell for a nearly infinite amount of time, both his body and mind were rusty.
Some players might think that Gil is finally making an appearance without his conceited attitude, but that attitude is part of his default character (I’m sure you didn’t know…).
The difficult of clearing the game with each Servant depends on their “cheatability.” As far as Gil is concerned, until his cheat-tier Noble Phantasm is unlocked, the game is about the same difficulty as when using Red Saber.
His Noble Phantasm causes an insane amount of damage, to the point where I’m rather worried about the balance of the latter half of the game.
Battles might end up being pretty bad if they are just Gil attacks → enemy insta-dead.
So that’s pretty much the story about our AUO1. Since he is an allied Servant, his relationship with the protagonist eventually reaches the point of mutual trust, and after engaging in some casual chit-chat his Secret Garden will become available to you.
Also, since Gil has not been incarnated into the alternate history world of EXTRA, the modern civilization of EXTRA has not influenced him in the slightest. In CCC he appears as a more neutral incarnation based on the Age of Gods version of Gilgamesh, and one might occasionally see his more casual, personal side.

Translator’s Notes
  1. ^ Sounds like eiyuuou 英雄王 = King of Heroes.
Fate/EXTRA Material: Encyclopedia of Fate/EXTRA

A Servant in Altera’s army. He has declared himself her second-in-command.
The King of Uruk, capital of ancient Mesopotamia.
He appears in ancient Mesopotamian legends, beginning with the Epic of Gilgamesh, which is said to be the oldest epic poem.
He is born of a union between god and man, and lays claim to all of the world’s myriad treasures as the “King of Heroes.”
Like Iskandar, he is a Top Servant.
Although the other two (knight-class) Servants of his rank were summoned by the Moon Cell, Gilgamesh appeared in this land of his own volition by ripping apart the border (when it fluctuated) inside SE.RA.PH that separates the Near Side of the moon from the Far Side.
(Note: Typically only those of 〇〇〇〇 class possess the skill to descend on the world of its own volition, but in the Extra Universe this is just barely within the rules.)
He has no connection to the Heroic Spirit Altera, but does have a previous connection with the White Titan on Earth, and so he lends his aid just this once in order to fulfill an obligation he made in the past.
He also has memories of the events that occurred on the Far Side of the Moon. However, neither the Main Character nor Altera know that this is the biggest reason for him joining Altera’s side.

Fate/EXTELLA material: Encyclopedia of Fate EXTELLA