You were fighting Muzan the Demon king for a while. Until Muzan wants to get serious so Muzan adopt a more monstrous and battle-esque form, with a dark-red scale-like mass covering most of his body (prominently on his limbs, his forehead, and the entirety of his lower body), featuring sharp-toothed wide mouths all over of his body, and longer pale white hair. The sharp toothed jaws located all over his body in this form

“Come. And face your fate, demon slayer.”