the pale king filled all of his vessel babies with void in hopes of them being completely "hollow", so the radiance couldn't dwell on their thoughts and emotions and infect them. that's why he yeeted all the ones that expressed emotions. the hollow knight was finally a vessel that was completely hollow, but the pale King being the pale king f**ked the whole mission up by training, fathering, and loving the hollow knight making it feel love for him, which the radiance clinged on to to infect it. but the king didn't know that so he still f**ked the spider and asked the jellyfish and other thingy and sealed the knight in.