Nullstone

Found within the anvil and hastland mountains, Nullstone is a deep grey stone with swirls of lighter composite almost like one would see with well forged steel. Nullstone is an extremely heavy stone, comparable to marble in its density. Nullstone uniquely negates magic. Spells cast on Nullstone fizzle out completely and attempts to magically pass through it completely fail. Not anti-magic field, Nullstone stops spells but if one were in a room made of nullstone they would still be able to cast - the spells merely wouldn't be able to pass through the stone. This renders teleportation spells and even planar travel spells mute within their confines, as a person cannot magically travel outside or through nullstone. 
Nullstones unique composition has led to its study and use in antimagic weapons and containment. Nullstone cores are often used on antimagic devices such as collars or cuffs which have been imbued with the ability to cut one off from magic. Nullstone is often also used to create doors or locks which one doesn't want to be effected by magic.

Type

Stone