Not that it makes much difference now, but....
I’m I the only one who wondered why the Night King wasn’t fried to a crisp by Drogon’s dragon fire?
After all, supposedly the only way to kill a white walker is with fire or Valyrien Steel. So, why did it take a Valyrien dagger when a scorching blast from Drogon didn’t even slow him down?
Was it just to continue the drama, or did he possibly have some Targaryen blood in him? HMMMMMM???????
Wights can be destroyed by fire, but White Walkers are resistant to fire due to the extreme cold they radiate. This as was shown at Hardhome and also outside the cave in “The Door”. White Walkers can be killed by dragon glass or Valyrian steel. The Night King’s power over ice and cold was why Melisandre had a hard time lighting the trench on fire.
Bran said that he wasn’t sure if dragon fire would have any effect on the Night King, because it hadn’t been tried before.
I do not think the Night King has any Targaryen blood, because he was one of the First Men and was created approximately 10,000 years prior to the events in the TV show. The Targaryens only came to Westeros about 300 years before the War of the Five Kings.
However, it is possible that he is related to the Starks in some way. The Starks claim to be descended from the First Men.