The Cult of Cold Flame is a radical group of wizards who served as an enemy to various DC heroes such as John Constantine, Zatanna, Timothy Hunter and others.
Vertigo
The Cult first appeared in Neil Gaiman's The Books of Magic mini-series. Timothy Hunter, the boy destined to become the greatest mage of his time, has attracted their interest and they wish to harm him for their own gains. The Trenchcoat Brigade saves him from various attempts on his life and are mentioned to be battling them in India where they are mostly destroyed.
New 52
In the new DC reboot, the Cold Flame retuned as a powerful groupfounded by some of the most powerful sorcerers in the DCU such as an evil Zatara, Sargon and Tannarak. Mister E, a member of the Trenchcoat Brigade and enemy of the Cult in the previous Universe, now served as one of their founder and leader.
It was also revealed in Justice League Dark #0 that John Constantine and Zatanna's mentor Nick Necro is also a member.