While I'm thinking about Kaeya lore, sort of relevant to the theory I posted last night is the 'sacrificial lamb' discourse I see about Kaeya every so often, which isn't really serious at all but is still pretty interesting to me. I think that while Kaeya is certainly intended as a sacrifice, a pawn in a much larger plot, he's also far too defiant. The typical image of a sacrificial lamb is one of innocence. The lamb is docile. It does not know what lies before it, and accepts the rope and does not question the knife. But Kaeya has always known. Ever since childhood, I think, Kaeya has known exactly what they think he is, and he is distrustful, wary, and resentful. He certainly won't go quietly if he can help it.
Kaeya's lore, the character of Hagen, and the Waltharius as a source
DISCLAIMER: This has been floating around in my head for a while now, I'm not really a lore player and I don't keep up too much with other theories, so forgive me if I'm simply repeating what others have already said! This is also a pretty long post, so again, my apologies! This isn't really my area of expertise, so my knowledge regarding these myths and stories in particular is only the product of brief research rather than general study (please bear with!).
The Nibelungenlied and other related media (for example, the Wagner opera) seem to be pretty well-trodden ground for a lot of Genshin theorists, and I've seen a lot of other theorists point out connections between Kaeya and the character of Hagen, or Hogni, a one-eyed descendent of the dwarf Alberich. The connection is strong and one I largely agree with - but the character of Hagen also appears elsewhere, and in a way that is equally as relevant to Kaeya as the Hagen in Der Ring Das Nibelungen.
The Nibelungenlied, the medieval German epic itself, is usually dated to 1200 from what I can tell. Of course, as with many other medieval and ancient stories, many of the characters of the Nibelungenlied can be found in other works, and told in other stories. Briefly found in the Nibelungenlied is one Walter of Aquitaine, a character of pure legend, who has an epic tale of his own, the Waltharius. This is typically dated to before the Nibelungenlied, and resembles the story in quite a few ways (according to Wikipedia, it also resembles a lot of the Aeneid, which will be my next bit of Kaeya research). Here's the Wikipedia summary of the plot:
A number of things stick out to me here. First of all, Hagano is certainly tied to the mythical character of Hagen, who Kaeya is likely based on. In the Waltharius Hagano is explicitly not of noble blood, which contradicts many other depictions of Hagen, who is royalty. The Alberich family were confirmed many moons ago in the Hidden Strife event to be regents, not of royal blood themselves. Kaeya of course is riddled with royal imagery, but there is a very crucial distinction to be made between inheriting royal blood versus becoming royalty due to regency.
(Source: Hidden Strife/Story | Genshin Impact Wiki | Fandom)
To me, this indicates that Kaeya's character is not simply based on the Hagen of the Nibelungenlied, but also of the Waltharius - it could be coincidence, but it's pretty suspicious that the one characterisation I can find of Hagen where he is not explicit royalty lines up with Genshin canon here. Also interesting is the 'brothers-in-arms' relationship that Hagano and Waltharius are described as having. Sound familiar at all? Equally damning is this little tidbit:
Considering that Hidden Strife also confirmed that Diluc injured (but not blinded, I know) Kaeya in their fight, then we can certainly take Walter of Aquitaine as an inspiration for Diluc. I'm very aware that there is a strange mish-mashing of sources going on here, and that this piece of information did not come straight from the Waltharius itself. But, I would add that so much of medieval legend is just weird mish-mashing, and that so much of Genshin lore is also just weird mish-mashing. So, I think it's safe to say we can take a few liberties here and there when the links are so strong.
The story of Hagano in the Waltharius, then becomes so interesting when you look at it with Kaeya and Diluc in mind. Hagano is given as a hostage in his youth to bring about peace, meets Waltharius, becomes his close friend, but is forced to fight him when the politics of his past complicate his present circumstances. This is insanely close to Kaeya's story - he was left in Mondstadt for some unknown purpose, befriended Diluc, and according to Mona's prophecy, will have his past catch up with him and be forced to make a decision.
In the Waltharius, two other things happen: despite the conflict, Hagano and Waltharius remain friends. Hagano also survives, something many other iterations of Hagen do not (one particularly ominous ending for Hagen is found in the Wagner opera, where he dies trying to take back the Rhinegold upon the orders of his father, Alberich...). But, if Genshin is following the Waltharius alongside other stories, then we can certainly be optimistic about Kaeya's fate! After all, in his turn as Prince Qubad in his Hangout Event, Qubad is cut off from his homeland after defying his father, but survives.
Another key point from the Waltharius is that Hagano is a hostage in the court of Attila the Hun. So many Kaeya lovers, myself included, are fascinated by the question of his placement in Mondstadt. Why did his father leave him there? Why is he the 'last hope'? What is his purpose? It seems that even Kaeya does not know, given his speculation in the quest, Caribert:
(Source: Destined Encounter | Genshin Impact Wiki | Fandom)
Unless Kaeya is lying - which is entirely possible - then I struggle to believe that Kaeya is, at least consciously, any kind of spy or active agent of Khaenri'ah. To me, this is a moment of rare truth and vulnerability for Kaeya. It seems like genuine speculation on his behalf, and if he were saying this to hide that he might be a spy, this is a very strange, roundabout way of doing so, and doesn't really line up with how we know Kaeya to lie and deflect.
If Kaeya was placed in Mondstadt as a hostage, just like Hagano was, then I think a lot of questions will be answered. I would clarify that being a hostage in the middle ages is very different to being a hostage nowadays. It does not always indicate a violent kidnapping, as we might think, but instead can be a sort of job, performed to enforce an agreement between parties. The only requirement of a hostage is that they stay alive to remain as the insurance keeping an agreement together. If this is true of Kaeya, then 1) it explains the 'purpose' of Kaeya being in Mondstadt, since his job is literally just to stay alive, and he wouldn't need to actually know about any of this, 2) being a political hostage would only become problematic when relationships between the two parties are strained. Not least because of Mona's prophecy, but also just because of where the game is headed, I certainly think tensions between Khaenri'ah/the Abyss Order and their opponents are on the cards. It explains why Kaeya has been able to live in peace until now.
Kaeya also has some interesting symbolism in his design that lends itself to my theory: being a peacock, a largely flightless bird in a nation of freedom, wind, wings, and flight, contrasted with his brother, an owl, a bird of prey, the one-winged cape, the strange vision, the cuff-like bracelets he wears. All these things allude to a lack of freedom. Of course, this could just be because he feels trapped by fate, but it's worth a mention.
But, this does beg the question: who is Kaeya a hostage of? I can't say exactly, since I'm not up to date with a lot of Genshin's newer lore, but I would posit that Istaroth seems to have domain in Mondstadt, is one of the Shades, a particular enemy of Khaenri'ah and the Abyss Order, and if some weird time travel bullshit happened, it might explain why Kaeya is seemingly unafflicted by any of Khaenri'ah's various curses and also alive in present-day Mondstadt. I also do not believe I can safely argue as to why Kaeya is a hostage, or how something like that came about, since so much of the Alberich & Khaenri'ah lore hasn't been released, but who knows where things will go in the future?
