Smoke Parasite

"He's right," said Miphon. "Stay away for the moment. The smoke is parasitic, but the light will weaken it. Soon it'll trouble him less, and be too weak to batten onto anything else."
"How do I get rid of it?" said Blackwood.
"You can't," said Miphon.

-Book 1, The Wizards and the Warriors (Wizard War)

A cold grey smoke that reacts to heat. Usually emanating from the mouth and lungs of one of it's victims.

As the name suggests, the smoke parasite is parasitic, entering a hosts lungs after they inhale it, usually in underground places such as caves and tunnels. There is likely no cure, although some believe that a mix of Dragon's blood and Human blood can cure any disease, including parasitic smoke. Remedies include exposing oneself to sunlight and breathing in the smoke and flames of a burning fire.