From Lost Fables Wiki
Blood coral is an extremely strange, and aggressively toxic form of life. Normally, just about anything which comes too near the dread metal cobalt simply perishes, while this coral flourishes, while in direct contact with the ore no less. Despite its danger, it is a very beautiful form of coral, coming in all sorts of colors.
Blood coral is extremely rare, appearing only underwater, and violently toxic. It is covered in thousands of tiny barbs, which introduce a flesh-eating enzyme into whatever unfortunate creature it hitches a ride in, violently and aggressively eating away at the flesh for several hours afterwards. All of this means that it is extremely difficult to harvest, even in the supremely rare facilities in which it is regularly grown. Generally speaking, it is done with long tongs and claws, trying to keep the coral as far away from anyone's flesh as possible.
There are essentially no uses of blood coral which are not violent in nature. Whether being made into arrowheads which devastate their targets or alchemical warding paint which partially flays those who walk through it, there is basically nothing nice you can do with this stuff. There are rumors of a blood coral-metal alloy in many alchemist's circles, but most regard these as mere stories. After all, one would have to possess the wealth of a Rehk-Ur god-king to even consider using the stuff normally, much less experimenting with it to see if such claims are true.