"Face of the Faceless" Diarmuid Ua Duibhne.
The adopted son of Aengus Mac Og, the god of love in Celtic mythology.
He was the chief warrior of Ireland's Fianna, and once protected Fionn and the rest of the Fianna at the Palace of the Rowan Wood.
According to legend, Diarmuid's beauty mark seduced Grainne, the wife of his lord, Fionn. Grainne used a spell to force Diarmuid to elope with her.
Though he struggled with it, in the end, he gave in.
Diarmuid fled with her for sixteen years, defeating countless enemies, until Fionn had no choice but to reconcile with him.
However, at the end of the story, Fionn laid a trap.
He led Diarmuid to his fated death, then refused twice to heal him.
To his very last breath, Diarmuid never hated Fionn. He died with only regret and sorrow.
He was famous for wielding five weapons in total: two swords, two spears, and a knife.
The weapons in his hands now appeared to be one sword and one spear.
Gae Dearg and Moralltach.
"It's a pleasure to meet you, great hero from Ireland, Diarmuid Ua Duibhne, Face of the Faceless."
Iori nodded and greeted him, then introduced himself.
"My name is Uchiha Iori. If you don't mind, just call me Iori."
It was quite strange. If you counted generations through his mother's side, Diarmuid, who had lived two centuries after Cú Chulainn,
was actually Cú Chulainn's great-grandfather. The generations of the mythical era were truly bizarre.
Diarmuid regarded Iori with some curiosity. He recognized that Iori had used Cú Chulainn's Gae Bolg earlier, but he had no idea who Iori was.
"Hey, Uchiha kid, what brings you here today? If you've got nothing important to do, why not join us for a drink? It's not every day we get a new member. Let's celebrate together."
Cú Chulainn called out. Usually, he was easygoing and generous, never one to fuss over small things. It was hard not to like him—a stark contrast to the bloodthirsty frenzy he displayed in battle.
Uchiha Iori smiled. He didn't like drinking, but he knew that bonding over drinks was a custom shared across eras and cultures.
He reluctantly declined. "Just call me Iori. I can't right now, though. There's about to be a war in my world."
"I came here to test the power of Gáe Bolg: Soaring Spear of Striking Death—to check its strength, range, and exact cost, so I can plan how to fight."
Iori explained the reason for his visit to Cú Chulainn. He needed to get a feel for the new skill's actual power.
Cú Chulainn nodded, showing that he understood.
"Oh, well, we'll see if there's time later."
He waved a hand, still smiling. For Heroic Spirits, time held little value. The daily routine of European Heroic Spirits was to eat the finest food, drink the strongest liquor, and fight the fiercest battles.
Uchiha Iori breathed a sigh of relief. He didn't like turning down people's kindness.
"Are you planning to test it on an open field, or find an opponent to fight?"
"Want to go?" Uchiha Iori asked, turning his gaze to Cú Chulainn with a slight smile. It might've been pretty dishonorable to fight the original with a knockoff, but it gave him a strange thrill.
Cú Chulainn irritably shook the spear in his hand.
"I told you, don't use my spear to fight me."
Then Cú Chulainn turned to Diarmuid. "Diarmuid, want to spar with him?"
Diarmuid smiled faintly and nodded.
"Of course. Let me see what you can do. I won't use Gae Dearg or Moralltach."
"I'll only use Beagalltach and Gae Buidhe."
Diarmuid said this as he put away the red sword and spear and swapped them for a yellow short sword and short spear.
According to legend, when Diarmuid believed an adventure truly put his life on the line, he would bring the great magic sword Moralltach and the magic spear Gae Dearg.
When he believed the danger was less serious, he would bring the magic sword Beagalltach and the magic spear Gae Buidhe.
In the myths, he died after being struck by a wild boar because he had brought only the latter pair.
"So, the reason you appeared wielding either two swords or two spears in the Holy Grail War was the class restrictions, after all."
"You're best at using a spear and a sword at the same time, right?"
Uchiha Iori asked. He'd learned about this when watching the anime, and now seemed like a good time to get the facts straight.
"That's right, but there's no class restricting me now. Don't underestimate me because of how I performed in the Holy Grail War." Diarmuid nodded, his words carrying a hint of warning.
"I'm in no position to underestimate anyone. But words are always empty. Let's settle this in battle." Iori swung his spear and surged forward, pushing off hard with his feet.
Gae Dearg
Rank: B → B+
Type: Anti-Unit Noble Phantasm
A sharp spear about two meters long that nullifies defenses made of magical energy.
Its attacks are especially effective against armor woven from magical energy. Any magical enhancement or additional abilities applied to weapons also lose all effect when they touch this spear.
Gae Dearg is a continuously active Noble Phantasm and requires no True Name Release to take effect.
It is a "Noble Phantasm killer" that can only be defended against by physical means.
It is a magic spear given to the adopted son of the Celtic god of love and youth, Diarmuid Ua Duibhne, by his adoptive father, the god of love Aengus, the greatest mage.
The runes inscribed on the red spear mean "yew (sacred tree)," "binding," "gift," "birch (abundance)," and "god of war (victory)."
Moralltach
Rank: B
Type: Anti-Unit Noble Phantasm
It is a divine sword that the sea god Manannán mac Lir once gave to his adoptive father, Aengus.
Legend says that a single swing can kill everyone on the battlefield who stands against the sword's wielder.
When its True Name is released, it leaps high into the air and attacks as it descends. It splits into three blades and crushes the enemy.
Gae Buidhe
Rank: B → B+
Type: Anti-Unit Noble Phantasm
A yellow short spear, 1.4 meters long, imbued with a curse that makes wounds impossible to heal.
Anyone wounded by this dangerous short spear suffers an irreparable injury.
Neither "healing Magecraft" nor "regenerative abilities" can remove the resulting "wounded state."
Gae Buidhe is a continuously active Noble Phantasm and requires no True Name Release to take effect.
The curse can only be removed by destroying the spear or killing its wielder.
It was a gift from the sea god Manannán mac Lir to Diarmuid Ua Duibhne.
Though the spear is extremely dangerous, its owner, Diarmuid, can stand on its tip without being harmed in the slightest.
The runes inscribed on the yellow spear mean "success," "hail (power)," "gift," "birch (abundance)," and "god of war (victory)."
Beagalltach
Rank: B
Type: Anti-Self Noble Phantasm
One of the weapons bestowed by the sea god Manannán, it takes the form of a short sword.
As a defensive Noble Phantasm, it raises its wielder's defense while also enhancing Diarmuid's abilities when he uses the magic sword Moralltach.