Mistfiend

A mistfiend is a dangerous gaseous being from the Nevernever. First appeared in Turn Coat.

Description
A mistfiend is a rare and dangerous gaseous being from the far reaches of the Nevernever.

It whips out misty and deadly tendrils toward any sources of light and cuts through anyone who gets in the way. Samuel Peabody laced it with Mordite which made it particulary deadly on contact. The first wizard it killed it cut completely in half in one swift stroke of a smoky tendril.

It was infused with mordite

Turn Coat
In Turn Coat, at Donald Morgan's trial, Harry Dresden accuses Peabody of being the real murderer of Aleron LaFortier and of framing Morgan. In order to escape, Peabody broke an ink bottle that freed a Mistfiend laced in mordite killing and wounding many of those attending Morgan's trial.

It took all of the Senior Council to contain it. Since most of the wizards present at Morgan's trial were LaFortier's supporters, they ended up being most of the wounded and killed by the Mistfiend. It caused an outcry of suspicion by LaFortier's supporters.