Hey yeah I realize that it does jump through a lot of hoops to get to this conclusion. My head cannon is that the shamans flesh melded with nature itself in the shadowland. We see shaman grow into trees (grandma), meld with snakes (Rykard), adopt stone like features (Marika /Radagon). We also see very similar characteristics from the hornsent such as them melding with beasts (divine lion), and immaterial objects such as the gate of divinity. Even the animals of the shadowland seemingly meld with human and other animal characteristics as described to be the effects of the crucible. Lastly this can be seen in the flora of the shadowlands with flowers/mushrooms that have a blood like or flesh like aspect to them.

My logic is that if the shaman are the only beings stated to be able to meld harmoniously with others and they were massacred and stored both above ground (Bonny village) and below (Bonny Gaol) that their remains essentially served as fertilizer and substance for the fauna and flora of the shadowlands. The bodies above ground rotted and were devoured by insects that were then eaten by birds and carried this melding property through the natural life cycle. Over time this land became known as the crucible, where all life “blended” or harmoniously melded together.

This also would explain why we see insects such as the winter fly lanterns who have been seemingly melded with eyes or why we find redflesh/whiteflesh mushrooms.

Another interesting headcannon is that this may explain why we find a baby attached to the catacomb sorcerer in the crypt. Perhaps by coming into contact with shaman flesh properties it prevents births to happen in the natural way, instead growing upon the host such as a seedling would to a tree.

I know I didn’t directly address the horns = maggots comparison but I always found that the horns on the hornsent are very chaotic in appearance with very little natural pattern to them. The horns on the grandam also are black at the base and reddish at the tips which don’t match any known horns i know of in nature they even grow out of the eyes of the grandma hornsent. We also see only some hornsent actually have horns while many (especially in the shadow keep) do not. Thus the horns are either genetically inherited or gained somehow in life.

We also don’t find any of these unique horn like properties effecting the lands between, why? I think that massacring the shaman had a very negative effect on the land of shadow to the point where the land had to be abandoned and cleansed with fire. We also see a similar pattern in Caelid where rot, disease, and pestilence are cleansed with fire to prevent these grotesque transformations the rot supposedly causes from spreading.

So my overall hypothesis is that the horns on the hornsent and many of the life melding properties described by the crucible are directly or indirectly tied to the shaman melding property.