It takes mythical Dragonglass to kill a white walker (obsidian in real life), heaps of which are in the Earth below Dragonstone castle, home of the Targaryens.
In this season’s Game of Thrones, on HBO Jon Snow travels from The Wall in the North, south to the Island of Dragonstone, to convince that Daenerys Targaryen that not only do white walkers exist, but that she needs to let him mine the Dragonglass to make weapons that will save humanity. Amid the tension of whether they’ll hook up, Snow ultimately gets the OK once she sees ancient cave drawings that depict white walkers:
A fan-made video posted to YouTube by a user with the handle Zouru shows what Jon Snow and his men from Castle Black could do if they had access to modern mining tools.
Game of Thrones airs Sundays on HBO, but you knew that already.