DevilCraft
A fictional form of craft introduced in the last book, it is can be used for many things. If ingested by Nephilim it will greatly increase their powers, but if infused into weapons it can cause the wound not to heal. And possible kill the Nephilim or even a Fallen Angel. In the book it is described as a blue liquid, or if infused into a weapon, the weapon would have a blue sheen. It has side effects like any regular drug, it will rot the users brain, and also has serious withdrawals, making them addicted to it