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.
- Forbeck, Matt, and David Noonan. Stronghold Builder's Guidebook. Renton, WA: Wizards of the Coast, 2002. Page 35.