In the Abyss, cataclysmic battles have raged for eons, laying down a sediment of iron, blood and spent magic. Abyssal Bloodiron is mined from thin deposits of mixed blood and ferrous mineral, compacted over the years, then forged at a low temperature to preserve its innate powers. Weapons forged of the metal usually appear dark except for their cutting edges, which are as red as freshly spilled blood.
A weapon forged of Abyssal Bloodiron is treated as a Cold Iron weapon, except that its wielder gains a +4 bonus when rolling to confirm a critical hit.
Abyssal Bloodiron has the same weight as iron or steel. A weapon made of Abyssal Bloodiron costs an additional 10,000 gp, and any magical enhancements cost an additional 2,000 gp, just as with Cold Iron. (The price includes 300 gp for the masterwork component.)
Abyssal Bloodiron has hardness 10 and 30 hit points per inch of thickness.
Source: Planar Handbook (Page 69)