Dark Steel

Dark Steel is used in the Underdark, and is not stable in sunlight.

Dark Steel is an enhanced steel alloy with a small amount of adamantium and radioactive materials. The steel performs well underground, but must save vs disintegration every day it is exposed to sunlight. Failure means that the weapon is permanently rendered useless and will break into small fragments when next struck with force. This happens because the radioactive materials' half-lives are significantly reduced when exposed to UV radiation, and therefore can no longer act as a bonding agent between the adamantium and ordinary steel.