Ok since I’ve been in the undertale fandom a while and never actually posted, here’s a good starter
The way I hc how skeletons work, since I don’t really like how ectoplasm looks in art I replace it with webbing
say the black stuff inbetween sans’s bones, is actually thick webbing meant to not hood it together but more so make it more defended.
if the rib gets snapped, in a situation in which the soul chamber would be completely exposed the webbing blocks it.
also ectoplasm looks weird on skeletons why do people give them t h I g h s.
anyway I imagine the soul isn’t actually super squishy and is instead covered in a thick hard membrane, and only things specialized to tear through it can actually harm it outside of battle.
Inside is pure magic, or DT in the case of humans, the fiber of a being is put in there but in the downside is a suuuuupppperrr good meal for things that CAN eat them.
the level of specific evolutionary traits need to tear through the membrane include:
teeth not to dissimilar to a big cats
holy shit we’re dead kinds of claws
and finally, mmmmm 100 grams of protein and iron, yes souls