After the latest episode, I have some doubt about what can kill a White Walker and why.
We know, as a fact, that both Valyrian Steel and dragonglass can kill White Walkers, and they have in common being forged by dragon fire, which I initially thought was the reason they had this power.
In the latest episode, though,
we see the Night King stand untouched in one of the arguably strongest breaths of dragon fire, made with the sole purpose of killing him
That scene gives me lots of doubt.
if dragon fire cannot kill White Walkers, why should things forged with it do it? We can argue Valyrian steel has been enchanted in the forging process, but weapons made from dragonglass have clearly not been, yet they have been shown to kill White Walkers. Why can't the dragon fire kill the White Walkers?