Obdurium

Obdurium is a a fantastically hard metal, even harder than adamantium or mithral. This incredibly rare metal represents the pinnacle of nonmagical metal strength. It is also extraodinarily expensive, costing ten times as much as carving stone walls and sixty times what a normal wooden wall would cost to build.

Obdurium is pale violet in color.

The doors leading to the Godtrap in Zagig's Prison beneath Castle Greyhawk are made of it.