The Corruption Explained (The Magnus Archives Entities) 

I wouldn’t say it’s as primal as those two and the flesh. I would say it’s a little bit more advanced, maybe on par with the Slaughter, The Stranger and say the Dark? Like it’s hovering in that liminal space between primal and semi primal?

With its domain over toxic relationships and identity, I think the Corruption can definitely beat the primal allegations. I do agree that most invocations of the corruption appear to be primal since they just "grab a foothold wherever and start growing" but it's just advanced enough that I think it escapes that handily.

I personally believe it’s more in the middle of the entities creation wise, probably only emerging around the time cities started to emerge, a bit before the eye, around the same time as the buried, deselation, and web, and a good bit younger than the hunt and dark

I would argue its basic for humans but not as quite as primal. A lot of animals don't really fully understand what is disguisting and what's not. Sort of like how a dog eats out the trash because it doesn't understand or something. Not to say animals can't find stuff gross, especially if they eat something bad tasting, I just don't think it would have the level of fear necessary early on. Plus, when it comes to humans the concept of hygiene has gotten better, more complex, and evolved overtime and likewise fear of what is dirty has gotten strong and more impactful as we gain a better understanding of how unsanitary things can hurt us.

Genuinely. Sickness and parasitism have been around probably since close to the beginning of life on Earth, and whether through fear or other mechanisms, life has always needed ways to protect against parasites.

Oh absolutely. Ivy Meadows is one of those stories that fades into the background a bit, but when you put it front and centre to get a good look at it, you realise how deeply unsettling it actually is. Definitely has to be pieced together from a few different episodes, but it's worth it.

Hmmmmm... interesting! I actually really like that. Might even have been a pre-ritual, like the creation of Agnes, who knows.

It really is and, having spent a few weeks scouring the Corruption while researching this video, I really do think that the only thing even coming close was Prentiss' attack on the Institute, and that was snuffed out before it could even begin in earnest. MAYBE Amherst's attempt at melting an entire town, but that mostly seemed out of his own desires, not to service some greater eldritch god's attempt to emerge in reality. Maybe it was, and it certainly would be fitting, given it's what ends up "killing" (still not totally sure he's not out there somewhere as the first avatar of the Extinction) Dekker, but I feel like the description of Agape is just much more in line with the other Rituals we hear about. I think someone else here in the comments mentioned that the Corruption may not have Rituals per-se, so much as it just "pops up" whenever conditions suit it, and I definitely think that that could be the answer as well. Compared to the other Entities, the Corruption is simple, it's about insects and disgust, so it makes sense that it's Rituals are equally simple. Perhaps as a result of having simpler, smaller-scale Rituals, the Corruption is able to have more Ritual attempts at any given time, like a mould cropping up wherever its darkest and dampest. Since less "energy," or however Ritual attempts work, is being expended in each attempt, it may be easier for the Corruption to get to work on a new attempt, so maybe Agape, Amherst, and Prentiss were ALL trying smaller scale Rituals. Who knows, just a theory I saw down here that I'll definitely have to mention whenever I do the "recap" video.

Huhhh... that's actually a really fair point. Now you've got the cogs in my brain turning.