Summary of the Caster Cu Chulainn=Odin Theory

I've translated a blog post by a user named Orafu, who posted a summarized theory of why CasCu could be Odin. The following are all their opinions and information gathered by them (thank you Orafu). Obviously, there has been some debate about the plausibility of this theory, so I want to see on what you all think! (IMO, there are some good points and some questionable points, but I think it's a good read anyways.)

(Linked screenshots will be from FGO JP that was compiled within Orafu's blog, but I'll try to post TLs as needed since it's hard to get the FGO NA versions easily, assuming NA has already reached those reference points)

List of Suspicious Points

  • Doesn't give his True Name

  • Has memories at the time of his summoning

True Name

CasCu says “Oh, it's you guys! We met before right?” when he is summoned. It is believed that he was summoned with memories of what happened in Singularity F.

(Since there are cases such as Arash having memories of Sky Silver, it’s impossible to determine if this is because it was a Chaldean summon or if it was another reason.)

  • The Caster of Singularity F is not Cu Chulainn in the first place

The Caster of Fuyuki’s Holy Grail War in the first place was Solomon, not Cu Chulainn. Also, the Caster in Fuyuki’s Fifth War was Medea. Singularity F was stated to be the result of data colliding with one another.


This is from one of the interviews conducted on Nasu and Takeuchi, and how Nasu stated that there has indeed been data colliding with one another that resulted in CasCu as a Caster.

  • A game that never ends


“Isn’t it boring to play a game that never ends? For better or worse, it’s like you can’t move the pieces forward, yeah?” This may be related to the mystery of Singularity F (Orafu skips the discussion of Singularity F for now).

  • The two wolves in his Ascension


Odin has two wolves. They are Geri and Freki.

  • The statement of how there is no Cu Chulainn here


Caster Cu Chulainn’s comment in the Kara no Kyoukai event. It may be treated as a gag, but the statement “There is no Cu Chulainn here” can’t be dismissed when taking the Odin theory into consideration.


Ochd Deug Odin - Seal of the Great God

Rank: A Type: Anti-Fortress Range: 1~80 Maximum Targets: 500

Ochd Deug Odin. In modern terminology, it'd be called Matrix Wodan. It is a Noble Phantasm activated by chanting its true name and using all 18 primordial runes obtained from Scathach at the same time. The power of the rune possessed by the great Odin is released temporarily and deals inmense magic damage to the enemy camp. It also removes all buff effects from enemies, and reduces all their stats by 1 rank. In case of the enemy possessing passive NPs, these are cancelled for one or two turns.

An extremely powerful ultimate attack that is not utilized in FGO.

It's possible that usage restrictions could be set up by Odin, but the details will be left unknown here.

  • North American version of his Bond Craft Essence


==In the North American version, CasCu’s Bond Craft Essence is “Yggdrasil Tree”. Yggdrasil is the world tree in Norse mythology. There is a theory that the Ygg in Yggdrasil is a reference to another name of Odin, and that the original meaning of Yggdrasil is “Odin’s horse”.== Also, Yggdrasil is an ash tree. To begin with, the Celtic druids used ash trees, so it is natural that CasCu uses ash trees when he is a druid, but the fact that the English name is stated as Yggdrasil Tree makes it all the more suspicious.

  • CasCu in the Nordic field (Boudica’s 3rd Strengthening Quest)

Nordic Fields

  • The only one in the Singularity F Memorial Quest with a Class name instead of a True Name

4th anni

In the Memorial Quest, Cu Chulainn is the only one who has his Class name, Caster, used.

  • Human Order Reorganization statement in Valentine’s Day


During Valentine’s Day for his return gift scene, he talks about the Human Order Incineration and the Human Order Reorganization. It is clear that he has known about the Human Order Reorganization (the Lostbelts) for some time.


ForeverAll seasons!

CasCu said this in the same Valentine’s return gift scene. He has stated that he will not participate in festivals other than Halloween, but Elizabeth, who appeared in the Kamakura event, states that there will be a Spring, Summer, Autumn and Winter Halloween in 2021.

Therefore, it seems obvious that CasCu will appear this year. (The revival of Halloween is a foreshadowing disguised as a gag. The revival of Halloween in 2021 is a foreshadowing of 666).

  • The book “Scandinavia’s Beautiful Mountains” is being read by Cu Chulainn during the 2019 Valentine Event

Scandinavian Book

In one of the 2019 Valentine Event’s Free Quests, CasCu appeared as an enemyopen in new window, with the book he is reading being “Scandinavia’s Beautiful Mountains”open in new window.

This was stated in Scathach’s Interlude. The Lancer Cu Chulainn is not at his full power. The reason being that half of his Saint Graph is missing. In other words, it is possible that this other half is CasCu. Also, the Lancer Cu Chulainn didn’t know about the existence of CasCu.

In response, Mash wondered if the fact that they were divided into multiple Classes might have reduced Cu Chulainn’s power by half. However, this phenomenon is not seen in any other Servant except Cu Chulainn. Maybe CasCu has elements of Odin mixed in to maintain that Saint Graph. (Orafu points out the possibility of Odin clinging onto Cu Chulainn, who is the main body, with good intentions, like how Kagekiyo fused with Yoshitsune in the Kamakura Event).

  • 2nd LB Opening


He appeared in the opening for the latter half of the Lostbelt arc, and is expected to appear in LB6, where the Celts are almost certain to appear.

  • Didn’t appear in the Final Singularity

The Singularity F Servants didn’t come to the Final Singularity. Also, when Kinoko Nasu was hiding behind a Twitter account, he tweeted about Singularity F coming up when everyone forgets about it, so it is clear that the mystery behind Singularity F is involved. (Kinoko Nasu’s Twitter: This tweet was when Kinoko Nasu was on Twitter as Champignon, which is French for Mushroom. It’s not a private account, the name being used was Moro, and it was only discovered because he was tweeting information and behind-the-scenes stories about a Servant that was going to be strengthened, which only those involved should know about. This account has now been deleted. However, it was clear he was on Twitter based on his behaviour. Is this the age of great pirates looking for the One Piece called Kinoko Nasu’s Twitter account?)

  • It is essentially impossible for Cu Chulainn to be without the Martial Arts Disciplining in the Shadow Country Skill (before training) or Gae Bolg (after training)


Setanta Profile 3

Martial Arts Disciplining in the Shadow Country: B+

The days of training brought about by the Land of Shadows’ landlady - Scathach - had tempered Setanta’s mind and body and allowed him to reach completion as the peerless hero Cu Chulainn. Setanta possesses this Skill because his current Saint Graph’s mind and body is from the time of his training days (specifically, just before the end of his training). In the case that he truly materializes as the hero Cu Chulainn, he will no longer possess this Skill, but instead will possess the Noble Phantasm Gae Bolg.

(In other words, a situation where the materialized hero Cu Chulainn does not possess either this Skill or the Noble Phantasm Gae Bolg————should be essentially impossible.)

Setanta was implemented in FGOAC. In Setanta’s Profile Section 3, Setanta possesses the Martial Arts Disciplining in the Shadow Country Skill because he was summoned during the time he was in his training days. If he had finished his training, he would not have this Skill, but the Noble Phantasm Gae Bolg instead.

Thus, it is impossible to summon Cu Chulainn without this Skill or Gae Bolg.

  • In the case of Riyo’s drawings, the nose for Proto, Lancer and Alter Cus are the same, but the nose for CasCu is clearly different

  • A remark that he is getting smarter

Odin has gained wisdom in exchange for losing one eye. Also, when CasCu is wearing a hood in his standing poses, it looks intentional that he’s standing with one eye nearly not visible.

Why CasCu is Odin

  • Primordial Runes

The Primordial Runes came from Odin

  • Sun God Lugh -> Mercurius -> Mercurius is another name for Odin

Cu Chulainn is the son of the Sun God Lugh. And this Sun God, Lugh, was mentioned as “Mercurius (Latin for Mercury)” in Caesar’s Gallic Wars. And this divinity, “Mercurius”, may be another name for Odin. Therefore, Cu Chulainn is related to Odin through the syncretized process of Lugh = Mercurius = Odin. (The fact that Caesar himself was mentioned in the Kamakura Event could be seen as a foreshadowing).

  • Gae Bolg’s Original Prototype is Gungnir


This was Archer’s statement in FSN.

During the Lancer vs Archer fight, when Archer took on the attack of Gae Bolg with Rho Aias, he remarked “Your Gae Bolg surpassed the Original Gungnir.” It has been pointed out that Gungnir was the Original Prototype of Gae Bolg.

  • Foreshadowing of an enraged Cu Chulainn


Based on these foreshadowings, and combined with the recent mention of an enraged Cu Chulainn, the etymology of the name Odin is “the delirious one” or “the raging one”.

It was stated that the Cu Chulainn that would be summoned as his original/proper Berserker self is the enraged Cu Chulainn, so both “the delirious one” and “the raging one” can apply to Cu Chulainn.

To begin with, who is Odin?

Odin is the Chief God of Norse Mythology and a God of Storms.

He is a god of wisdom, death, war and magic.

He has an eight-legged horse called Sleipnir, and releases the crows Huginn and Muninn around the world to gather information. He has two wolves, Geri and Freki, by his feet.

He is often depicted as an old man in black robes, and because he is one of the main deities, there are many anecdotes about him. He has the Valkyries gather the souls of warriors into Valhalla. Eventually, he was eaten by a wolf named Fenrir, Loki’s child, during Ragnarok. (Fenrir appears as a Servant in the Fate/EXTRA Last Encore Drama CD, summoned by Misao Amari as the Rider Vanagandr. Vanagandr is another name for Fenrir.)

The reason why there has been many stories lately about the Gods of Storms and eight heads, such as Yamata no Orochi, Vritra, Minamoto no Raikou and Indra, may all be a foreshadowing for this God of Storm and the eight-legged Sleipnir.


Brynhildr was dispatched to the Tokyo Holy Grail War in 1991. Passage in Fragments of Sky Silver about why Brynhildr rampaged and aimed for Manaka (TL'd by RisingPhoenix who worked on the Fragments Translation):


“Strangely that was in the exact same way as when Lancer called the girl a “Drachen.” Despite also grasping at the emotions that he couldn’t even grasp himself, the little remaining ego, and the fragments of his consciousness that he had, made an extremely calm decision. The real reason Lancer, no, Brunhilde went rogue. The source of that, conducted herself like she had taken back her faculties as the daughter of a god.

Nigel: “It’s, you……!?”

This girl. This menace was trying to bring destruction to the world. She didn’t bat an eye on reaching the Root, and she was going to achieve her goal even if she had to offer all of creation as a sacrifice to it――――

In LB6, where 666’s shadow is strong, Odin’s involvement would make sense.

  • He created the Valkyries from the fragments of Sefar

Given that Odin used those fragments to create the Valkyries, there is a relationship between Altera and Brynhildr.

  • In LB2, Huginn and Muninn were dispatched to guide Chaldea

The crows that flew above them in LB2 were Odin’s messengers.

What are your thoughts? I do think that the writers have been building up on this mystery a lot in relation to Singularity F, or it could be one big red herring. I'm indifferent if CasCu does turn out to be Odin in disguised, but it's cool to revisit one of the plot points that hasn't been touched upon until very recently (where Setanta's release in FGOAC called into question CasCu's existence).