Dragonglass is a common name in Westeros for the substance known as obsidian, a form of volcanic glass. Along with Valyrian steel, it is one of the two known substances capable of killing White Walkers.
- Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock; it is hard and brittle; with very sharp edges, which were used in the past in cutting and piercing tools
- Obsidian is truth-enhancing. A strongly protective stone, it forms a shield against negativity. It blocks psychic attack and absorbs negative energies from the environment. Obsidian draws out mental stress and tension