User blog comment:Kogath/Monster Hunter XX Discussion/@comment-27120688-20170318201839

For those who don't know:


 * All old Deviants have 5 more G rank quests each.


 * The 6 new deviants only have the 5 G rank quests.


 * You must complete the 5 G rank quests for the 6 new deviants and have at least the original 10 quests  for each old deviant to unlock MD Diablos.

However, when you complete MD Diablos's quests, break HR, etc (not sure if there are other requirements)

There are HR100 locked deviant quests:

http://imgur.com/WXwyhjK

You can basically consider these even stronger than the G5 deviant quests you get in the game. I'm not sure if Hellblade is the only one, but its the only one I've seen.