i haven't seen many people talking about it but i find it so neat the shadow crystals are broken dreams, and make sense with the bosses in their contexts
like spamton finding the crystal in the neo body being that abandoned dream for it's artist throwing away the project, breaking off the dream, because having the actual body isn't feasible (at least in this universe). It'd also make Sneo smelling like "Rotten Glass" make more sense as the dream has been dead for awhile.
gerson found the shadow crystal in his desk, where he's kept and where alvin works, who's been struggling to write his own sermon and live up to the reputation of his father, but with susie carrying gerson's message, learns to latch onto that dream again.
pink says the body had the crystal when she got there, and i believe it's tied to the mad ghost possessing the figurine after seeing it but couldn't move in it, or it even could be tied to alphys who (presumably) gave asgore the doll in the first place but I'm more tied with the former.
i just think this context on the shadow crystals this chapter is so neat and opens up a sea of questions in what the shadow crystal attained from the knight means.
And as for what seam is making I think it's an item we'll use to counter the knight in the ending chapters.
