|Greyhawk magic item|
|First appearance||Return of the Eight' (1998).|
Oerthblood is the name given to a molten, dark red, ferrous metal. Once it has cooled, it is black, dense, easily enchanted and nearly impervious to damage.
Several famous magical artifacts found in the World of Greyhawk, such as Heward's Mystical Organ and parts of the infamous Machine of Lum the Mad are made from oerthblood which has been worked and then enchanted.
Beneath Castle Greyhawk, in its deepest and most guarded levels, lies the Oerth Stone, a quasi-sentient artifact rumored to be crafted entirely from the purest oerthblood ever found. Its powers are reputed to have played an essential role in Zagig Yragerne's elevation to demigodhood.
Oerthblood is dangerous to handle in its unworked form, typically constructs and other automatons are used in mining it because of their ability to withstand its unpredictable magical radiations, as well as the heat and often poisonous gases that are given off by impurities while in its molten form.
Several locations around the Flanaess are reputed to have deposits of oerthblood. The most famous is the archmage Tenser's castle, the Fortress of Unknown Depths. Deep under the castle is an ancient mechanism called the Endless Well. It is from this device that most of the raw oerthblood presently found in magical arms, armor, devices and artifacts around the Flanaess was taken. Oerthblood has also been found in the mines beneath the city of Irongate.
- Holian, Gary, and Denis Tetreault. "Irongate: City of Stairs." Dragon #351. Bellevue, WA: Paizo Publishing, 2007.