this doesn;t make sense that grimmel has killed off all the nightfuries expect toothless he wasn't counting but as soon the nightfuries ehard the news of theyre species being endangered so they hid away to the hidden world grimmel thought 'hey i killed them all"so its a possiblity that they have hidden away from grimmel as grimmel is unaware of it the nightfuries stopped hiding when grimmel died of drowning(possibly)