[Everything] What are the odds that the Night King has ______ ?

What are the odds that the Night King has dragons in his army of the undead? We've seen the Night King with undead horses and giants so why not dragons? I assume much of his army are the dead from the previous war thousands of years ago? Were dragons around during the previous war with the White Walkers? If any of the dragons are killed in battle this season, what are the odds that we see them again but fighting for the Night King? Dany seeing her own Dragons being used against her would be quite the emotional roller coaster for "The Mother of Dragons".