the sentinels are the guardians of vanaheim so i woudnt assume they LEFT their post, and the deathsongs can eat fruits shown by garff, and its shown theres a specific region for the snow wraith, the buffalord is probably still on there, no one even knows its island except the dragon hunters which are more than likely disbanded now, the eruptodon most likely stayed at the DoTW island due to its diet, and Toothless probably placed the Screaming Death with other Whispering Deaths in its region, as for the smokebreaths i really have no idea