this was a showerthought, hear me out chat, unless I went batshit insane like everyone else and got some things wrong you can correct me BUT

Is it entirely possible that Thrain the Sentinel Knight is erased from Irminsul?

But how so? Didn't Mavuika find some info about Thrain and linked it to Capitano in the 5.3 quest?

https://preview.redd.it/lrz6ttvydf3h1.png?width=837&format=png&auto=webp&s=e156136a576b90b2cd8b1bebebb87816383ed3c9

Well, actually brings me to my first point,

1. Mavuika mentioned in the 6.6 quest that her records are stored in the Night Kingdom which are disconnected to the Ley Lines

Which could possibly mean that she deduced The Captain's identity using records said by people who are stored in the Night Kingdom, not the Ley Lines

But why is this relevant?

It's because we don't have a single fucking clue about what Thrain/Capitano did at all in the entirety of fucking Teyvat, like HES THE FIRST HARBINGER WHY IS THERE COMPLETELY NO FEATS, but every fuckass always says hes strong oh wow good one wheres the feats

which is so weird knowing we actual proof about what Zandik did all over the world (Mondstat- Ursa bullshit, Inazuma- Taratatsuna crap , Sumeru- homeland, Nod-Krai- fuckass experiment), it's not even only Dottore like we also have other stuff for other harbingers all over the world like random ass flavor texts, etc that I'm too lazy to collect because this is this a crack theory

But Capitano having no info outside of Khaenri'ah, Snezhnaya and Natlan? AINT NO WAY MAN.

2. Mavuika doesn't remember him/know him at all??, a 7 foot Khaenri'ahn chad strong as an Archon with his fuckass platoon that came from THE Nation that was ground zero for the cataclysm?

dementia?

Like are we taking the piss? mUst bE thE maSk, nah. hes deleted from irminsul trust me chat

TLDR: All Thrain info we got so far are only from himself, the people trapped inside him, and info technically from people who are preserved in the Night Kingdom

now theres a chance this gets debunked in 7.x flavor text around the world which is why i am posting this now xd, but theres also a chance nobody else knows wtf a Thrain is, I'd say this might be a insane crack theory