Obdurium
Obdurium is a pale violet metal which is harder than adamantine. This incredibly rare metal represents the pinnacle of nonmagical metal strength. It is also extraordinarily expensive, costing ten times as much as carving stone walls and sixty times what a normal wooden wall would cost to build.
The doors leading to the Godtrap in Zagig's Prison beneath Castle Greyhawk are made of obdurium.
Bibliography
- Forbeck, Matt, and David Noonan. Stronghold Builder's Guidebook. Renton, WA: Wizards of the Coast, 2002. Page 35.
- Bulmahn, Jason, James Jacobs, and Erik Mona. Expedition to the Ruins of Greyhawk. Renton, WA: Wizards of the Coast, 2007. Page 186.