I realized I forgot some. This should be all.
Abe no Seimei: Priest for Emperor Toba who discovered Tamamo's fox ears.
Achilles: Greek demigod and student of Chiron. Iskandar claims to be his descendent.
Agravain: A Knight of the Round Table and Mordred's half-brother.
Aife: Scáthach's twin sister. Connla's mother.
Amaterasu: AKA Golden White Face. Japanese sun goddess. Full form of Tamamo-no-Mae. Was defeated by Sefar in 12,000 BC. Able to classify as a Beast.
Anchin: Past target of infatuation for Kiyohime. Tried hiding from her in a temple bell but was burned alive by her.
Andreias Amarantos - Amaranth of the Brave. Anti-Personnel (Self) Noble Phantasm of Achilles. Continuously active. Rejects all attacks from those lacking Divinity or aren't from a Divine Construct. "Friendly" attacks can bypass it. (ex: A vampire bite can be seen as making a comrade of the victim) Damaging Achilles' heel will disable it until he gets resummoned along with slowing him down by 70%.
Aoko Aozaki: Touko's sister. Possesses the fifth True Magic, Magic Blue.
Arturia "Arthur" Pendragon: AKA King Arthur. Hid the fact she's a woman from her subjects. King of Knights and founder of Camelot. Mordred's father.
Avalon: The Everdistant Utopia. Name for the sheath for King Arthur's sword, Excalibur. Essentially passively grants the wielder immortality if supplied with mana. Was lost before Camlann.
Ayamachi: Twin sword of Kotowari. In Yukari Mishakuji's possession.
Bazett Fraga McRemitz: Enforcer from Ireland's Mage's Association. Original Master of Cú Chulainn in the Fifth Fuyuki Holy Grail War. Possesses Fragarach.
Brionac: The Five Roaring Stars. A spear possessed by Lugh.
Camlann: Site of a single-day battle between King Arthur' army and Mordred's army.
Clan Calatin - Multi-headed monster comprised of a wizard and his 27 sons. Killed by Cú Chulainn during the Táin Bó Cúailnge.
Chronus: Greek god of time. Chiron's father.
Conchobar mac Nessa: King of Ulster during Cú Chulainn's time and Deichtine's brother. In Emain Macha.
Connla: Son of Cú Chulainn and Aife. Was killed at age eight by Cú Chulainn.
Curruid: Phantasmal sea monster. One of its bones was used to make Gáe Bolg after it was killed by Coinchenn.
Deichtine: Cú Chulainn's mother.
Emer: Cú Chulainn's wife and his source of emotional support.
Failinis: Wolfdog owned by Lugh. Large and invincible at night, small as a lapdog and a ball of fire during the day.
Ferdiad: From Connacht. Cú Chulainn's best friend and trained alongside him in the Land of Shadows. Killed by Cú Chulainn during the Táin Bó Cúailnge.
Fujino Asagami: Descendent of the Asakami family. Has powerful telekinesis, manifested as the Mystic Eyes of Distortion. Rendered blind after twisting and destroying the entire Broad Bridge in Mifune.
Galahad: Knight of the Round Table and Lancelot's son.
Gate - Hole created by the Holy Grail, a path to the Root.
Gawain: A Knight of the Round Table and Mordred's half-brother. A horrible cook.
Genji Kagutsu: Red King before Mikoto Suoh. Caused a Damocles Down in 1999, killed as a result.
Ghost Liner- Familiar comprised of mana. As such, it's reliant on mana to stay alive. Servants are in this category.
Gungnir: Declaration of the Great God. Spear of the Norse chief god Odin and what Gáe Bolg was based off.
Heracles: Greek demigod and student of Chiron. Accidentally shot Chiron with a poisoned arrow after completing his fourth labor.
Initiation for Red Clansmen - The person takes the Red King's hand while red aura covers it. If it rejects the person they get burned, severely or to death. Being accepted grants fire power.
Jin Habari: Blue King before Reisi Munakata. Killed in 1999 by Gouki Zenjou.
Kay: Knight of the Round Table. Raised Arturia Pendragon.
Kirei Kotomine: Priest and Overseer for the Fifth Fuyuki Holy Grail War. Stole ownership of Cú Chulainn from Bazett.
König Project: Research project on the Dresden Slate in Dresden in 1945, headed by Adolf K. Weismann, to create superpowered beings.
Kotowari: 500-year-old sword passed down through the Miwa lineage. Has enough Mystery to cut Okada Izou.
Koushi Mizuchi: Gold Clansman. Essentially tortured Anna before she joined HOMRA.
Lugaid: Fatally wounded Cú Chulainn with Gáe Bolg during Connacht's second invasion of Ulster.
Medb: Queen of Connacht. Came up with the plan to kill Cú Chulainn.
Medusa: Gorgon sister banished to the Shapeless Isle with her two sisters, Stheno and Euryale. Has Mystic Eyes of Petrification.
Misaya Reiroukan: Master of Cú Chulainn during the Second Tokyo Holy Grail War. Was killed by Cú Chulainn during the War after she succumbed to her curse.
Morgan le Fay: King Arthur's sister and Mordred's mother.
Philyra: Nymph who was impregnated by Chronus in horse form. Chiron's mother.
Ryouma Sakamoto: Central figure of the Meijin Restoration. Former friend of Okada Izou but sold him out.
Scáthach: Ruler of the Land of Shadows and Cú Chulainn's teacher. Unable to die and taught Cú Chulainn how to use Gáe Bolg in the hopes he'd kill her.
Táin Bó Cúailnge: Cattle Raid of Cooley. Seven-year war where Cú Chulainn single-handedly fought off the army of Connacht.
