Item from A Song of Ice and Fire by George R.R. Martin
Volcanic obsidian — the only substance besides Valyrian steel that can kill White Walkers and their wight armies, found in vast deposits beneath Dragonstone.
Dragonglass spent thousands of years being a curiosity — pretty volcanic rock that maesters collected and children played with — until the White Walkers returned and it became the most strategically important material in the world. Sam Tarly killed a White Walker with a dragonglass dagger at the Fist of the First Men, the first such kill in eight thousand years, and that discovery transformed the entire war. The Children of the Forest used dragonglass to create the White Walkers in the first place, which gives the material a terrible symmetry — the weapon and the wound share the same substance. Dragonstone's deposits became the arsenal that armed the living for the Battle of Winterfell. In any scene where dragonglass appears, the stakes shift from political to existential — it means the dead are coming, and someone is preparing to fight them.
Jet-black volcanic glass with a glossy, razor-sharp surface that fractures into wicked edges. It can be knapped into arrowheads, daggers, and spearpoints. It shatters on impact against armor but passes through White Walker flesh like fire through paper, causing them to crystallize and explode.
Also known as: dragonglass, obsidian, frozen fire