Mordite

Mordite or Deathstone, is congealed antilife not of our World. It's first seen in Death Masks.

Death Masks
In Death Masks, Harry Dresden describes it as congealed antilife, "a chip would make nuclear waste look like second hand smoke." Not from our reality, it's from Outside and sensitive to applied will.

In reaction to a bug placed into the box with it, it vaguely formed an inky cloud that floated up out of the box about the size of a baby's head. It had dozens of shadow tendrils that held the scorpion, violet flickers of flame burned the shell till it crumbled to dust. According to Thomas Raith, it looks like someone spray-painted a soap bubble and gave it tentacles.

Turn Coat
In Turn Coat, it is described as weapons-grade Deathstone that can rip the life force out of everything it touches.

Death Masks
In Death Masks, the Archive provides a sphere of mordite for the Test of Wills, duel between Paolo Ortega and Harry Dresden. To demonstrate what it does, Ivy puts a scorpion into the box with it.

For the duel, the ball that the Archive has formed has an enchantment to bind the mordite particles in place. It's sensitive to applied will. The duelists face each other with the mordite ball between then and will it to their opponent. The duel ends when one is devoured by it.

Turn Coat
In Turn Coat, Samuel Peabody smashes an ink pot on the floor releasing a mistfiend laced in mordite, killing and wounding many of those attending Donald Morgan's trial with frightening smoky tendrils that could slice a human in half in a blink. The Senior Council, all of them, use applied will to contain it. Peabody infused it with mordite.

Skin Game
In Skin Game, Hades wears a crown of mordite.