Really, at this point in time I wouldn't put it pass George to have the Night's King kill everyone and rule Westeros in an everlasting night.
House Lannister
House Stark
House Baratheon
House Greyjoy
House Tully
House Tyrell
House Targaryen
The Night's Watch (not really a House, but whatever)
House Martell
The Realm (look at you, being all noble and trout)
House Other (please specify below)
Really, at this point in time I wouldn't put it pass George to have the Night's King kill everyone and rule Westeros in an everlasting night.