how did the night king get a dragon

The Night King got a dragon by killing Viserion beyond the Wall and then raising him as one of the undead. That’s why Viserion fights for him later, but he’s not a normal dragon anymore; he’s an undead dragon, often called a wight dragon.

What happened

In Game of Thrones , the Night King’s real goal in the Season 7 finale was to get a dragon, and he succeeds after Viserion dies during the expedition beyond the Wall. Once Viserion is dead, the Night King uses his powers to reanimate him, turning him into a weapon for the army of the dead.

Why it matters

That undead dragon is what helps the Night King destroy the Wall later, because Viserion’s blue fire can breach it. So the “how” is simple: kill the dragon, then raise it back up as undead.

Common confusion

People sometimes call Viserion an “ice dragon,” but the better description is undead dragon or wight dragon, not a separate dragon species. The icy look comes from his undead state, not from him being a naturally born ice dragon.