The Cathedral of the Deep has these enemies that respawn immediately. They're a type of enemy that shows up a lot in these games: a human body riddled with and/or controlled by and/or in a symbiotic relationship with parasitic bugs that behaves, to a large degree, like the Venom symbiote from Spiderman, only internal.
The demonic rockworms from the first game took a diverging path after the first game. I don't know that these are definitely the same things the Chaos Servants were breeding, but the second game points out that they do evolve to fit their environment. The DS2 rockworms are pretty straightforward, but the DS1 blight-born parasites Engyi etc are breeding are much smaller, which Quelana and Salaman's whole thing was refining uncontrollable Chaos down to useable pyromancy. So it seems like Engyi is continuing Quelaag and the Fair Lady's work in refining exploding fire giants down to Tauruses and Capras.
But that's not why we're here. We're here to talk about the gross, pukey graveyard bastards' are able to respawn indefinitely.
Who else has this strange power? (you have to imagine I'm holding up a Human Effigy right now)
These poor guys' are what happened to us, the Lordran Chosen Undead, after Vendrick came through. Solaire didn't become the rockworm, the rockworm became Solaire. Vendrick took the Lords Souls to Drangleic, and from that point the Firelinking Ritual's diminishing returns would fall off a cliff. Untethered from the bonfire the hollows die, are rejected by Death, and return to their home; the graves in this instance. We don't really get to see what happens when our character respawns at a bonfire, but without a darksign or a bonfire this is what it would probably look like.
The Grave Wardens, just like in the second game, are tasked with keeping the undying from getting unruly. Unlike the second game, where Dark mostly remains tranquil and serene, Dark in the third game needs to be kept at bay at all costs, because it was poisoned and driven mad. Multiple times.
Let's back up. There is no "Dark Soul" in Lothric the way there was in Lordran and Drangleic, there are no humanity sprites. The strength of the Unkindled comes from embers, which look like burnt sprites. There's still the Abyss, only this time it's evolved.
The Sky is Dark in the Past, While the Fire was Out.
The Seal of Fire, the burning ring around the Dark Sign, I think, prevents Pus of Man outbreaks, as well as keeps the carrier bound to the bonfire. I think the Seal failed when the fire went out, which if that didn't happen when Vendrick 'stole fire from the Gods', then it would have happened shortly after. In Untended we seem to be very far in the past, before the Unkindled began their quest, but after Lothric had sent Gundyr on his mission.
Which is one of the reasons we're back in this godsforsaken graveyard outside the Cathedral.
You meet siegward and patches here the first time, idk that it's important except to each other, since Patches, after finally going hollow, starts to emulate Seigward.
Patches is effectively guarding Rosaria, and we know that at least some (all) Patches thirst for powerful women. Siegward makes Estes soup which is condensed from undead corpses, because undeads love estus.
Patches is friendly with the mangrubs, although I don't think Patches is a finger. I think Patches cares about the cathedral, or some aspect of its history, and he's clearly been fueled by a Morgot-like grudge against everything since at least Gwyndolin was put in charge, as his connection to the White seems to date to before the giants were enslaved.
He, Patches, is called Unbreakable because for whatever reason he's got an invincible hollow. My guess is that his grudge started very shortly after Nameless was put in charge.
Both Seigward and Patches seem to like giants. Too nice. That's these peoples' problem.
The mangrubs, I would argue, are really gross, and seem to be the result of overindulgence in rebirth.
Here's what's going on with them.
Rebirth, Rosaria's version, whether or not it directly causes the infestation, does cause an infected host vessel to demonize, becoming blended with the demonic/parasitic half. Only instead of a bull or goat or even a flaming mad meltspider demon you got these fucking worms.
But here we are, fighting demons in a church. The thing that was the fire of life: the Phoenix, Ever Renewing. Even after the fires have gone out.
Well done Engyi.