|Title:|| The Fake Spiral Sword|
Fake Helix Sword (English version of Extra)
Caladbolg II: The Fake Spiral Sword (偽・螺旋剣, Gi Rasenken?) is a modified version of the original Caladbolg using Reinforcement. Archer encountered the original sword at some point during his life, adding it to the numerous Noble Phantasms stored in Unlimited Blade Works and allowing him to modify it to suit his fighting style. He projects it to be used as an arrow rather than a sword, with the improvements aimed to make use of it as an A-rank Broken Phantasm. He chants the first line of Unlimited Blade Works' incantation before firing it and, despite being renamed with the "II", he still only chants "Caladbolg" to activate it. When utilized as a close-combat weapon, he thrusts it to pierce the opponent. Gilgamesh also owns the prototype of Caladbolg, which is stored inside the Gate of Babylon.
The blade of the sword coils into a spiral that can penetrate any target by creating a twisting distortion in space when fired. When fired at Caster, it is powerful enough to easily break through her magical defenses simply as an aftereffect of it being purposely fired at an area far away from her. Shirou believes that, even if she had tried to teleport away from the attack, she would have simply been twisted along with the space as well. After being intercepted by Berserker, it creates a large explosion capable of razing a cemetery and engulfing it in flames. It's true use as a sword is to create a sword of light that stretches from the magic sword like a rainbow.
The original is the demonic sword possessed by the hero of Ireland, Fergus mac Róich in Celtic mythology. The former king of Ulster and foster-father of Cú Chulainn, Fergus was tricked out of his kingship and later allied with Ulser's enemy nation, Connacht. He cornered the enemy king who betrayed him during the decisive battle between the lands, but he was prevented from killing his target. He redirected his rage at the undesired turn of events upon three hills by utilizing Caladbolg to cleanly blast the off the tops of the hills like a long rainbow. It is considered to be the natural enemy of Cú Chulainn, due to having a geis placed on himself making it his duty to be defeated once by the sword if the wielder is Ulster-born. There is also a theory that it is the same as Caledfwlch of Welsh mythology, making it a prototype of Excalibur.
 Fate/EXTRA material - Encyclopedia: The Reborn Sword of Victory [Noble Phantasm], p.163 English | Japanese
The Reborn Sword of Victory [Noble Phantasm]
Gawain's Anti-Army Noble Phantasm. A Pseudo-Sun is contained in the hilt.
A holy sword in King Arthur's legends, it is the sister sword to Excalibur. If Excalibur is a sword that destroys castles, this sword destroys the enemy army.
If King Arthur's holy sword collects the light of the stars, Sir Gawain's holy sword represents the rays of heat from the sun.
Unlike Excalibur's centralized attack, Galatine is a broad wave, radiation-type attack that completely annihilates the enemy army. Like Excalibur, the original owner is a Maiden of the Lake. Hidden in Excalibur's shadow, it's a holy sword rarely mentioned in the legends.
In the remaining legends, it is similar to its owner, Gawain, and shows its greatest power at noon, the unsurpassed shaprness of the edge is said to become visible. That sharpness sliced clean through the shield and chainmail of the enemy, the Saracen soldier Priamus.
As Arthur has the providence of the night (Alto, Artemis, the pedigree of the goddess of the moon), Gawain is the knight who receives the blessing of the sun.
That special characteristic is reflected in the Noble Phantasm, which is like the rays of heat from the sun. Caladbolg is the prototype of Galatine, like a long rainbow, and cleanly sliced off the top of a hill with its full power.
It was a sword of light that stretched from the magic sword like a rainbow. Galatine is similar; with a motion like drawing a sword, and the pseudo sun inside and the magical energy put into it, the attack extends as far as it is possible to visualize the blade of the sword.
That is to say...about 13 kilometers or so.
 Fate/complete material II: Character Material - Weapons: Caladbolg II, p.128 English | Japanese
Caladbolg is the demonic sword wielded by the Irish hero Fergus mac Róich in Celtic mythology. The version that Archer projects has been altered to improve its function as an arrow.
In the legends, Fergus mac Róich was the former king of Ulster and foster-father of the hero Cú Chulainn. However, he was tricked out of his kingship, and later allied with Connacht, an enemy of Ulster. During the decisive battle between Connacht and Ulster, Fergus was able to corner the enemy king who had betrayed him, but was prevented from killing him. It is said that he redirected his rage at this turn of events upon three hills, using Caladbolg to blast their tops clean off.
Cú Chulainn is affected by a geis that makes it his duty to be defeated once by the sword so long as the wielder is Ulster-born. For that reason, it could be said to be his natural enemy.
Also, there is a theory that the Caladbolg from Celtic mythology is the same sword as the Caledfwlch from Welsh mythology, making it a prototype of Excalibur.