Didn't know about that Corruption theory before (and didn't wanna reblog the post for spoilers) but now I'm curious, what other theories did people have while the show was still airing? I joined the fandom around 160 so anything before that is a mystery to me.
Referencing this post (beware, it has spoilers for The Magnus Protocol).
Oh goodness, so so many. Only a few that I remembered off the top of my head, but I spent some time today trawling the depths of my "magnus archives speculation/analysis" tag and found a couple more fun ones.
Most of the ones I did remember are either still popular headcanons (Web!Martin), or actually turned out to be canon (Jonah!Elias). The Gertrude one always stuck in my head because it's very silly on the surface but also draws attention to the fact of like - how was her skin still in good enough condition to wear after being buried for months? (And Lietner's too, for that matter). Was Nikola just wearing really tattered rotten shreds???
Anyway. Some that I remembered, which all relate to Martin for some reason:
Backup Archivist: Heading into the Unknowing, Elias had Martin reading statements specifically to train him to be a stand in Archivist in case Jon died. Also included sub-theories that he could end up able to compel people on his own, share the role with Jon, or take over entirely if the show pulled a bait-and-switch and Martin was the real protagonist all along.
Who's the Father?: Every single possible theory about who Martin's dad was and what implications that could have on the show, from Leitner to Elias to Peter Lukes to that one dude Peter banished to the Lonely in his statement in 159.
Schwartzwald Cousins: Albrecht von Closen says he and Clara/Carla had trouble having kids in his first statement, but in a later episode says they have two boys. Part 1 of the theory was that the kids were actually avatars who'd emerged from the mausoleum after Albrecht disturbed it, and been adopted by the childless couple. Part 2 was - well - it's canon that Gerry is descended from one of these kids. The theory was, what if Martin was descended from the other? Gerry seems to have some Eye powers linked to his heritage and upbringing, so it was speculated that Martin might turn out to have some as well and be important to either Elias's plans, or to thwarting him (this tied into the Backup Archivist theory nicely). A sub-theory was that they were significantly closer cousins, Martin's mum's maiden name had been Keay, and Martin K. Blackwood was Martin Keay Blackwood all along.
And the ones that I found in the tag (credit in brackets):
Martin’s mum was a runaway Lukas (@/centaurianthropology, here)
The lighter was linked to the Desolation (@agnesmontague) + an addition by me that I'm so proud of in hindsight - "I think the web design pretty much confirms that it’s linked to the Web, but if it’s the Desolation as well, might it be linked to the other occasions we’ve seen those two powers interact? Namely, the ever mysterious Hill Top Road?" (Here)
Another of my posts that I'm delighted to reread (here) reminded me of the many, many, "what's up with the tapes?" theories. I remember "the tapes are sent by the Web", "the tapes are sent by Elias", "the tapes are manifestated unconsciously by Jon" (my personal favorite, sadly disproven), and I think there were also some "the tapes are Gertrude's ghost" posts???
Elias was the Eye the same way Michael was the Spiral - Gertrude sacrificed him to stop the Watcher's Crown (@/statementbegins, here)
Also reading through these is reminding me that there was a stretch where we were calling the Vast and Lonely the "Void" and "Isolation", which I love.
This is just a select few posts from 2018, so there's a lot more under the tag if you're interested in looking! Link below, copy and paste into a web (lol) browser because the archive (lmao) page doesn't work on the app.
https://cirrus-grey.tumblr.com/archive/tagged/magnus%20archives%20speculation%2Fanalysis
If anyone else remembers other old theories please feel free to drop them in the notes! I know there were so many more that I don't have saved.