User blog comment:Kogath/Monster Hunter: World Discussion/@comment-6050823-20170921022042/@comment-6050823-20170921023559

Nergigante is constantly regenerating its skin as it attacks and is being stroke by hunters. It will slowly grow white spikes on certain body parts, which harden overtime. Hunters must try to break the white spikes before they harden. Once they have hardened, its attacks deal more damage.